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Severe acute respiratory syndrome coronavirus 2, coronavirus disease 2019 (COVID-19)-induced infection can be associated with a coagulopathy, findings consistent with infection-induced inflammatory changes as observed in patients with disseminated intravascular coagulopathy (DIC). The lack of prior immunity to COVID-19 has resulted in large numbers of infected patients across the globe and uncertainty regarding management of the complications that arise in the course of this viral illness. The lungs are the target organ for COVID-19; patients develop acute lung injury that can progress to respiratory failure, although multiorgan failure can also occur. The initial coagulopathy of COVID-19 presents with prominent elevation of D-dimer and fibrin/fibrinogen-degradation products, whereas abnormalities in prothrombin time, partial thromboplastin time, and platelet counts are relatively uncommon in initial presentations. Coagulation test screening, including the measurement of D-dimer and fibrinogen levels, is suggested. COVID-19–associated coagulopathy should be managed as it would be for any critically ill patient, following the established practice of using thromboembolic prophylaxis for critically ill hospitalized patients, and standard supportive care measures for those with sepsis-induced coagulopathy or DIC. Although D-dimer, sepsis physiology, and consumptive coagulopathy are indicators of mortality, current data do not suggest the use of full-intensity anticoagulation doses unless otherwise clinically indicated. Even though there is an associated coagulopathy with COVID-19, bleeding manifestations, even in those with DIC, have not been reported. If bleeding does occur, standard guidelines for the management of DIC and bleeding should be followed.

Background: A previously unknown beta-coronavirus was discovered through the use of unbiased sequencing in samples from patients with pneumonia. The virus was named as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) by the international committee for the classification of viruses (ICTV). The disease caused by this virus was named as coronavirus disease 2019 (COVID-19). In addition to pulmonary manifestations, hematological changes such as lymphocytopenia, thrombocytopenia, and coagulation dysfunction can also be found in COVID-19 patients, and the mechanism is still unclear. Case data and methods: A total of 633 COVID-19 patients from Wuhan hospital of China were retrospectively analyzed. Clinical case data of all patients were collected, including gender, age, chronic underlying diseases, outcome, and blood laboratory test results. The hematological features of COVID-19 patients and the factors affecting their outcome were analyzed. Results: Of 633 patients with COVID-19, the median age was 62 years (interquartile range, IQR, 51.0-70.0) and 330 (52%) were men. Lymphocytopenia (lymphocyte count, 1.0 ×109 / L [IQR, 0.7-1.4]) occurred in 317/607 patients (52%), thrombocytopenia (platelet count Conclusion: Hematological changes are common in patients with COVID-19. The early stage of the disease is mainly characterized by lymphocytopenia, thrombocytopenia, and the late stage may be characterized by more severe lymphocytopenia, even neutrophils elevation, elevated C-reactive protein, and severe coagulation disorder. The pathogenesis may be mediated by a direct viral infection and/or indirect immunopathology. Disclosures No relevant conflicts of interest to declare.

During warfarin management, prothrombin time (PT) based PT-INR variability is partly due to clinically inconsequential fluctuations of factor (F) VII. The new Fiix-PT and Fiix-normalized ratio (Fiix-NR), unlike PT-INR, is only affected by reduced FII and FX. Starting July 1st 2016 we replaced PT-INR monitoring of warfarin with Fiix-NR in our patients. Using interrupted time series methods, we retrospectively assessed if this affected thromboembolism (TE) and major bleeding (MB) incidence during 12 months prior to and 18 months after the replacement, months 13-18 being predefined as transitional months. The dynamic cohort comprised all our service´s 2,667 maintenance phase warfarin patients managed at any time during the 30 months. Using two-segmented regression, a breakpoint in total TE monthly incidence became evident six months after laboratory monitoring test replacement, followed by 56% reduction in TE incidence (from 2.82% to 1.23% per patient year, P=0.019 by ANOVA). Three-segmented regression found no significant TE incidence trend (slope +0.03) prior to test replacement but during months 13-18 and 19-30 the TE incidence gradually decreased (slope -0.12; R2=0.20;P=0.007). Based on segmented regressions, MB incidence (2.79% ppy) did not differ pre- or post-intervention. Incidence comparison during the 12 month Fiix- and PT-periods confirmed a statistically significant 55-62% reduction in TE. Fiix-monitoring reduced testing, dose adjustments and normalized ratio variability, and prolonged testing intervals and time in range. We conclude that ignoring FVII during Fiix-NR monitoring in real world practice stabilizes the anticoagulant effect of warfarin and associates with major reduction in thromboembolism without increasing bleeding.

Introduction An increasing number of evidence have reported the association of COVID-19 with increased incidence of thrombotic events. High incidences were initially reported in critically ill COVID-19 patients, but subsequently an increased incidence was also noticed in non-critically ill general ward patients. This has led to a universal recommendation of thromboprophylaxis for all COVID-19 patients by ASH and ISTH. As the data on COVID-19 and thrombosis continue to develop and evolve, we examined the data in two aspects. Firstly, other non-SARS-CoV-2 viral respiratory infections have also been reported to be associated with thrombotic events, be it arterial or venous. Thus, we aimed to compare the thrombotic rates between these two groups of patients directly to hopefully ascertain the actual thrombotic tendency in COVID-19 infections. Secondly, global hemostatic assays such as thromboelastogram and clot waveform analysis (CWA) have been used to demonstrate hypercoagulability in COVID-19 patients, albeit in a small group of patients and only in the critically ill. Incorporating these laboratory results into the management of thromboprophylaxis in COVID-19 is an attractive notion but more data and studies are definitely needed. Here, we evaluate the dynamic changes of hemostatic assays in patients with COVID-19 to better understand the overall coagulation profiles of COVID-19 infection. Methods We performed a single center, retrospective cohort study. All consecutive patients admitted to our hospital between 15 January and 10 April 2020 that were tested positive for COVID-19 or other non-SARS-CoV-2 respiratory viruses were included in our study. The main coagulation assays studied were prothrombin time and activated partial thromboplastin time and its associated CWA, min1, min2 and max2. Findings We included a total of 181 COVID-19 patients and 165 patients with non-SARS-CoV-2 respiratory viral infections. The respiratory viruses were rhinovirus (n=65), influenza A and B (n=46), adenovirus (n=13), human coronavirus 229E/NL63/OC43 (n=15), human enterovirus (n=3), metapneumovirus (n=6), parainfluenza virus 1 to 4 (n=11), respiratory syncytial virus (n=6) and human bocavirus 1 to 4 (n=0). The median age of COVID-19 patients was 37 (interquartile range [IQR], 30.5-51 years) versus 35 (IQR, 29-51.5) in the non-SAR-CoV-2 respiratory viruses group (P=0.12). Comorbidities, assessed by Charlson score, was also not statistically different between both groups (median score 0 (IQR, 0-1) in both groups, P=0.39). Majority of our patients had relatively mild infection as reflected by the low proportions of them requiring oxygen supplementation (11.0% in COVID-19 vs 4.8% in non-SARS-COV-2, P=0.035). COVID-19 patients had longer hospital stay (7 days (IQR, 5.5-13) vs 3 days (IQR, 2-3), P Conclusion The thrombotic rates were low in both groups and did not differ significantly between COVID-19 and Non-SARS-CoV-2 patients. Nonetheless, our analysis of hemostatic parameters demonstrated hypercoagulability in COVID-19 as a dynamic process with the risk highest when the patients are critically ill. These changes in hemostasis could be detected by CWA. With our findings, we suggest that a more individualized thromboprophylaxis approach, considering clinical and laboratory factors, is probably preferred over universal pharmacological thromboprophylaxis for all hospitalized COVID-19 patients and warrants further research. Disclosures Lee: Sanofi: Honoraria, Other: travel grants; Pfizer: Membership on an entity's Board of Directors or advisory committees; Bayer: Membership on an entity's Board of Directors or advisory committees, Other: travel grants ; Medtronics: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees.

Background: Extracorporeal membrane oxygenation (ECMO) is a salvage therapy for critically ill children and adults. Hematologic complications, such as hemorrhage and thrombosis, are the major complications in ECMO. The contact of blood with the tubing of the circuit, lines, blood pump, and oxygenator all contribute to the process. Most patients require anticoagulation while on ECMO. According to the international summary of Extracorporeal Life Support Organization (ELSO) registry in 2017, patients on ECMO consist of 69% neonate and pediatric patients (Neo 44.8%, Peds 24.1%, Adult 31.1%). Contributors to the risk of bleeding include excessive heparin use for systemic anticoagulation, consumption of coagulation factors, low fibrinogen levels, thrombocytopenia, platelet dysfunction, and hyperfibrinolysis, among others. This gives the appearance of a consumptive coagulopathy, the hallmark of which is hypofibrinogenemia. Fibrinogen replacement is most efficiently done with cryoprecipitate (cryo) or fibrinogen concentrate, while fresh frozen plasma (FFP) has a low and variable fibrinogen content. Cryo and FFP may contribute to volume expansion and have other prothrombotic factors which could contribute to thrombotic complications. We performed a retrospective analysis of pediatric and adult patients who presented for ECMO to evaluate management of low fibrinogen and bleeding and thrombotic complications. Methods: Data was reviewed for 11 adult and 12 pediatric consecutive patients who received ECMO prior to June 1st, 2019. Time on ECMO (hours), type of ECMO, indication, presence of bleeding or thrombotic complications during ECMO, and use of therapeutic anticoagulation was collected. Laboratory data included platelet counts, hemoglobin, fibrinogen activity, antithrombin activity, prothrombin time, and partial thromboplastin time. Transfusion data was also collected for amount of packed red blood cells (PRBC), platelets, FFP, and cryo transfused. Data were analyzed to evaluate when fibrinogen was low and if cryo was given. According to our institutional guideline, the fibrinogen activity goal is >100 mg/dL and >200 mg/dL if bleeding. Bleeding and/or clotting complications were also noted. Data: There were 24 runs of ECMO evaluated (11 adults, 12 children), including VA and VV, lasting from 65-1343 hours. One child had 2 runs of ECMO. The majority were VA (13/24; 54%) with 33% (8/24) VV and 13% (3/24) combined VA/VV (all occurred in children). Therapeutic anticoagulation was given in 17/24 (71%) overall, but 92% (12/13) of pediatric cases. Bleeding and/or clotting complicated 17 (71%) runs. Overall, bleeding occurred in 13 (54%) runs and thrombosis in 12 (50%). Of these events, 8 (33%) runs had both bleeding and thrombosis. Bleeding occurred in 8/11 (73%) adults and 5/12 (42%) children. Bleeding and/or thrombus occurred more often with longer ECMO runs, but affected all runs longer than 250 hours (12/24, 50%). While on ECMO, the fibrinogen activity was below 100 mg/dL at some point in 11/24 (46%) of runs. Of those 11, only 6 (55%) received cryo in response to the fibrinogen activity. Cryo was more likely to be given if both a low fibrinogen and bleeding were present. Even with bleeding episodes and fibrinogen activities Conclusions: Almost half (45%) of the patients evaluated had low fibrinogen levels at some point while on ECMO. Despite cryoprecipitate being standard replacement at our institution for low fibrinogen, only 55% of those patients received cryo in response to the low level. Therefore, 21% (5/24) of all cases were not specifically treated for their low fibrinogen value. Bleeding and/or thrombotic complications are common with ECMO. Further study to determine if fibrinogen replacement or lack thereof contributes to these complications and guide management of fibrinogen deficiency in ECMO patients is warranted. Figure Disclosures No relevant conflicts of interest to declare.

Background: End stage renal disease (ESRD) patients on chronic hemodialysis (HD) repeatedly have their blood exposed to artificial surfaces within the hemodialysis circuit, which triggers contact system-initiated coagulation. Clot formation within the HD circuit results in blood loss, decreased HD efficiency, and device circuit failure. Heparin reduces circuit clotting but it is not tolerated by all patients. Mounting experimental data suggest that contact system inhibition is antithrombotic without significantly compromising hemostasis. AB023 is a unique recombinant anti-factor (F) XI antibody that interferes with the interactions of FXI and FXII without inhibiting FXI activation by thrombin or the activation of FIX by activated FXI. This study evaluated the safety, tolerability, pharmacokinetics, and preliminary efficacy of AB023 in patients with ESRD on chronic HD. Methods: In this phase 2, randomized, double-blind, placebo-controlled, single-administration study, AB023 (0.25 or 0.5 mg/kg) or placebo was injected into the HD circuit of 24 ESRD patients at the start of heparin-free HD (NCT03612856). All patients underwent three pre-dose HD procedures and four monitored post-dose HD sessions. In total, the study encompassed 168 individual HD sessions, 72 of which occurred pre-dose and 96 of which occurred post-dose. Safety parameters, including time to hemostasis at HD access site, prothrombin time, physical examinations, vital signs, electrocardiograms, clinical chemistry, immunogenicity and other adverse events (AEs), were recorded. Clotting within the hemodialyzer circuit was assessed using a visual clotting scale by investigators who were blinded to treatment. The frequency of circuit clot obstructions requiring dialyzer exchange was also recorded. Pharmacokinetic and pharmacodynamic parameters, including activated partial thromboplastin times, were also assessed. The study was approved by an ethics review board and all subjects provided written informed consent. Results: AB023 demonstrated a favorable safety profile in ESRD patients. No drug-related AEs were noted. Clinically relevant bleeding did not occur in any patient, and the time to hemostasis at the HD access site was unchanged after AB023 administration. As expected, the aPTT was prolonged after AB023 administration, reaching saturation at both dose levels (about 2-fold prolongation) immediately after dosing, and remaining prolonged for up to 9 days with the high dose. Compared with pretreatment, the frequency of occlusive events requiring circuit exchange decreased by 68% and 50% in subjects given the 0.25 and 0.5 mg/kg AB023 respectively, while the number of occlusive events was numerically unchanged in the placebo arm. Likewise, the number of saline flushes required to maintain circuit patency decreased by 44% and 85%, and the incidence of high-grade clotting in the hemodialyzer as assessed by visual scoring decreased by 15% and 43% on day 1, 8% and 35% by day 3, and 0% and 19% by day 5 in the 0.25 and 0.5 mg/kg cohorts, respectively. Conclusions: Anticoagulation with AB023 was well-tolerated and reduced clot formation within the HD circuit of ESRD patients. These findings suggest that inhibiting contact system activation could reduce medical device-initiated blood clot formation in patients. Disclosures Lorentz: Aronora, Inc.: Current Employment. Verbout:Aronora, Inc.: Current Employment. Shatzel:Aronora, Inc.: Consultancy. Wallisch:Aronora, Inc.: Current Employment. Markway:Aronora, Inc.: Current Employment. Tucker:Aronora, Inc.: Current Employment. Gruber:Aronora, Inc.: Current Employment, Current equity holder in private company.

Introduction & Aim: Hemophilia A (HA) is an X-linked disorder caused by an absence or a reduction of coagulation factor VIII. Patients with HA often suffer from spontaneous bleeding within the musculoskeletal system, such as hemarthrosis. Hemarthrosis is caused by bleeding into joint spaces affecting the synovium, synovial blood vessels as well as cartilage and bone tissues. Current prophylactic treatments are not always effective and hemophilia patients can experience breakthrough bleeds. Recently, we demonstrated that inhibition of protein S (PS), a natural anticoagulant, controls coagulation and constitutes a potential therapeutic target in hemophilia (Blood 2018, 131:1360-1371). Here, we aim to translate our findings using small interfering RNA conjugated to an N-acetylgalactosamine (GalNAc) cluster to target Pros1 gene expression (GalNAc-PS siRNA) in vivo and exclusively in hepatocytes. siRNAs conjugated to a GalNAc cluster bind to asialoglycoprotein receptors expressed predominantly by hepatocytes thereby providing a potentially safe, specific and efficient delivery technology for therapeutic molecules. Methods & Results: Forty-two days after subcutaneous (s.c.) injection of GalNAc-PS siRNA (3mg/kg), wild-type (WT) mice were alive and did not display overt disseminated intravascular coagulation (DIC). In a second study in WT mice, DIC parameters assessed fourteen days after treatment with either 5mg/kg GalNAc-PS siRNA or with vehicle were also comparable between the two groups (platelet count: 578±284 vs 725±186 G/L, p>0.9, n=4-6; prothrombin time: 9.0±0.4 vs 8.9±0.3 seconds, p>0.9, n=4-6; fibrinogen: 1.5±0.5 vs 1.8±0.4 g/L, p>0.85, n=5-6; thrombin anti-thrombin complexes, TAT: 71±63 vs 115±34 μg/L, p>0.9, n=2-4) supporting that GalNAc-PS siRNA treatment can be safe. At the same time, mice treated with GalNAc-PS siRNA displayed lower plasma PS level compared to mice receiving the vehicle (52±12 vs 100±11 %, p To assess if targeting PS using GalNAc-siRNA-PS protects mice from acute hemarthrosis (AH), we applied an AH model to F8-/- mice. Five days after injecting a single dose of 5mg/kg GalNAc-PS s.c., right knees were injured using a 30 gauge-needle and knee diameters were measured 72 hours later. Macroscopically, vehicle treated F8-/- mice developed extensive bleeding in injured knees as compared to GalNAc-siRNA-PS treated mice. Scores for intra-articular bleeding (2.4±0.9 vs 1.0±0.7, p=0.035, n=5-9) and synovial hyperplasia (2.4±0.9 vs 0.6±0.9, p=0.027, n=5-9) were higher in F8-/- mice treated by vehicle than in those treated by GalNAc-PS-siRNA. Moreover, knee joint swelling was reduced in GalNAc-siRNA-PS treated mice compared to those treated by vehicle (0.14±0.15 vs 0.78±0.50 mm, p=0.025, n=7-10). As expected, PS plasma levels were lower in GalNAc-PS siRNA treated mice compared to those which received vehicle (63±9 vs 101±19% of WT PS antigen level, p0.9, n=7-12; prothrombin time: 8.5±0.3 vs 8.4±0.3 seconds, p>0.9, n=4-13; fibrinogen: 2.7±0.6 vs 3.0±0.8 g/L, p=0.73, n=7-12 and TAT: 33±42 vs 45±66 μg/L, p>0.9, n=6-10). Conclusion: These data provide the first evidence that using a GalNAc-siRNA conjugate to modulate Pros1 gene expression is well tolerated and has the ability to reduce plasma PS level and protect F8-/- mice from AH pointing to PS targeting using GalNAc-siRNA-PS as a new valuable therapeutic approach for hemophilia. Further analysis to understand if the inhibition of PS influences also the inflammatory processes causing the hemophilic arthropathy is ongoing. Disclosures Schaeper: Silence Therapeutics GmbH: Current Employment. Dames:Silence Therapeutics: Current Employment. Eisermann:Silence Therapeutics: Current Employment.

Introduction: In patients with SARS-CoV-2 COVID-19 infection elevated D-dimers are associated with a poor prognosis. Although suggestive of DIC, the majority of patients do not fulfil ISTH criteria for DIC. Studies have demonstrated that when compared to D-dimer, fibrin monomers are more sensitive and specific when differentiating overt DIC from non-overt DIC. Our special coagulation laboratory (SCL) routinely measures soluble fibrin monomer complex (SFMC) as part of our DIC profile in samples with elevated D-dimers. Here we aimed to investigate the percentage of patients with COVID-19 infection with elevated SFMC as performed as part of the DIC profile. Methods: Between April 1st 2020 and July 26, 2020 inpatients at the Mayo Clinic Rochester, MN campus with COVID-19 infection who underwent DIC testing in SCL were identified through SCL database. Patients were excluded if SARS-CoV2 PCR results were not available in the Mayo Clinic electronic medical record (EMR). DIC profile components include prothrombin time (PT), activated partial thromboplastin time (APTT), thrombin time (TT), fibrinogen and D-dimer. Reflex SFMC is performed if D-dimer is elevated. Data abstracted from EMR included results of laboratory tests, date of COVID-19 symptom onset, date of SARS-CoV2 PCR positivity, and death within 30 days of hospital admission. The ISTH DIC score was calculated and patients were labeled as overt DIC or non-overt DIC based off of ISTH DIC score ≥5. Results: 35 patients (19 female), median age 59 years (28-91) met our study criteria DIC profiles were obtained 6.5 (1-37) days after COVID-19 symptom onset (n=33) with 28 obtained within 14 days of symptom onset. Time to DIC profile from SARS-CoV2 PCR testing was 4 (0-37) days (n=35) with 31 having testing completed within 14 days of PCR positivity. 8 patients were intubated during hospitalization and of the remaining 27, 67% required supplemental oxygen. 21/35 (60%) patients had an elevated fibrinogen (526.5 mg/dL (201-800)) while 19/35 (54%) had a prolonged PT (12.8 seconds (10.1-99.6) and 5/35 (14%) had a prolonged APTT (31 seconds (24-68)). 17 patients with prolonged PT and 3 patients with prolonged APTT had factor activity assays performed (Figure 1A). 9/35 (25%) had thrombocytopenia (230 x 109/L (12-709) and 27/35 (77%) patients had an elevated D-dimer (895 ng/ml FEU (220- >100,000). D-dimer was higher in males than in females (p: 0.049). Of those with elevated D-dimer only 5/27 (18.5%) had an elevated SFMC (5 mcg/ml (5- >1100) (Figure 1B). 4/35 (11%) patients had ISTH DIC scores ≥ 5 and all had score of 5. All of these patients had D-dimer > 2000 ng/ml while only 2 had elevated SFMC however SFMC in both of these patients was < 15 mcg/ml. Of these, one patient with SFMC of 12 mcg/ml had known cirrhosis and the other with an SFMC of 11 mcg/ml had acute decompensation and associated shock liver. This patient also had venous thrombosis 3 days prior to DIC profile and died from complications related to COVID-19 infection. Of the two other patients with high ISTH score and normal SFMC, one had previous chronic thrombocytopenia of < 50 x109/L while the other had concomitant admission for acute and recurrent pancreatitis in the setting of alcoholism with acute intoxication. Six patients died within 30 days of admission and in 2/5 performed SFMC was elevated (Figure1C). Conclusion: Compared to 77% of patients with elevated D-dimers, of those tested only 18.5 % of patients had elevated SFMC. It has been hypothesized that the elevated D-dimer noted in COVID-19 pulmonary infection is a direct consequence of acute lung injury and not overt DIC. Although preliminary, the small percentage of patients with overt DIC by ISTH criteria and normal SFMC in the majority of the current cohort support this hypothesis; however studies in a larger more controlled cohort are needed to confirm these findings. Disclosures Sridharan: Alexion: Honoraria. Pruthi:Merck: Honoraria; Instrumentation Laboratory: Honoraria; HEMA Biologics: Honoraria; Bayer Healthcare: Honoraria; Genentech Inc.: Honoraria; CSL Behring: Honoraria.

Venous thromboembolism is a common complication in patients with cancer, but only limited data are available in acute myeloid leukemia (AML). In a prospective study in a cohort of 272 adult patients (aged 18-65) and an independent validation cohort of 132 elderly adults (aged >60) with newly diagnosed AML, we assessed markers of disseminated intravascular coagulation (DIC) (fibrinogen, D-dimer, α-2-antiplasmin, antitrombin, prothrombin time, and platelet count) and the DIC score according the International Society of Thrombosis and Haemostasis and their associations with the occurrence of venous and arterial thrombosis during follow-up. The prevalence of thrombosis was 8.7% (4.7% venous, 4.0% arterial) in the younger adults over a median follow-up of 478 days and 10.4% (4.4% venous, 5.9% arterial) in elderly patients. Most thrombotic events (66%) occurred before the start of the second course of chemotherapy. The calculated DIC score significantly predicted venous and arterial thrombosis with a hazard ratio (HR) for a high DIC score (≥5) of 4.79 (1.71-13.45). These results were confirmed in the validation cohort of elderly patients with AML (HR 11.08 [3.23-38.06]). Among all DIC parameters, D-dimer levels are most predictive for thrombosis with an HR of 12.3 (3.39-42.64) in the first cohort and an HR of 7.82 (1.95-31.38) in validation cohort for a D-dimer >4 mg/L vs ≤4 mg/L. It is concluded that venous and arterial thrombosis may develop in ∼10% of AML patients treated with intensive chemotherapy, which to a large extent can be predicted by the presence of DIC at time of AML diagnosis.

Background: Bleeding and thrombosis remain the primary complications related to the use of extracorporeal membrane oxygenation (ECMO). To date, no single test or parameter has been identified to accurately predict the risk of these hemostatic complications. Thrombin generation may be the key marker for both thrombosis and bleeding, and may be influenced by inflammation. The aims of this study were to evaluate if novel laboratory tests including thrombin generation assay, neutrophil extracellular traps (NETs), microparticles (MPs), and red blood cell (RBC) membrane fragility/adhesion could better predict patients at risk for bleeding and/or thrombosis compared to routine laboratory tests. We hypothesized that ECMO related thrombosis is associated with increased thrombin generation and ECMO related bleeding is associated with decreased thrombin generation. Methods: An IRB approved prospective pilot study of patients requiring ECMO was conducted at Children's Hospital of Michigan. Patients were enrolled within 24 hours of ECMO cannulation after informed consent. Patients aged 0-17 years placed on venoarterial (VA) or venovenous (VV) ECMO were included. Patient demographics, baseline laboratory, clinical data, and novel assays were collected. Presented is the preliminary data of the first 16 patients enrolled. SPSS was used for data analysis. Results: Of the 16 patients, there were 9 males and 7 females with the majority being cannulated for primary respiratory etiologies. Median age was 8.5 months with 6 patients being neonates (38%). Twelve patients (75%) survived the ECMO run, and 11 patients (69%) survived to hospital discharge. Laboratory data was grouped based on "no event" (N=94), "bleeding event" (N=13) and "clotting event" (N=21) days. There were no differences in the number of RBC, fresh frozen plasma, or cryoprecipitate transfusions between events. Platelet transfusions were used at higher volumes in bleeding events, p=0.011. Platelet counts did not differ between groups, whereas fibrinogen levels were significantly lower on days of bleeding events, p≤0.001 (Figure 1A). There were no differences seen in the activated partial thromboplastin time (aPTT) or activated clotting time (ACT) which are routinely used for monitoring anticoagulation. However, the prothrombin time (PT) was significantly prolonged in bleeding events with a median of 16 seconds (p=0.001), which may be related to the lower fibrinogen levels (Figure 1B). Thrombin generation was assessed using the maximum rate of thrombin generation (MRTG) value from the thromboelastograph (TEG) generated velocity curve (Figure 1D). Bleeding events had a significantly lower median MRTG of 7.93 mm/min compared to 12.36 mm/min in the no event group and 12.14 mm/min in the clotting event group (p=0.004). The thrombin generation assay results are in process. NETs were analyzed using an ELISA to detect citrullinated histone-3 (CitH3) levels (ng/mL). There were no significant differences seen in our population, however there is a trend toward increased levels in thrombotic events (Figure 1E). Both absolute MPs and platelet MPs were significantly increased in clotting events compared to bleeding events, p=0.003 and p≤0.001 respectively (Figure 1C). In our population, there was no evidence that hemolysis played a role in thrombosis as assessed by flow based RBC mechanical fragility testing. Of note, flow based RBC adhesion showed a non-significant trend toward increased adhesion to P-selectin. This finding requires further investigation because P-selectin is a primary site for adhesion on endothelial cells and plays a crucial role in coagulation (Figure 1F). Conclusions: Bleeding events on ECMO are associated with increased mortality. Our findings suggest that lower fibrinogen levels, prolonged PT and decreased thrombin generation (as assessed by the TEG) are associated with an increased risk for major bleeding. Increased levels of NETs, MPs and RBC adhesion have a trend towards increased thrombotic events. Thus, although preliminary, our results suggest that novel laboratory tests were effective in identifying bleeding events, and the trends seen in thrombotic events may allow for the use of new medications to reduce clotting in ECMO. The results illustrate the challenges in monitoring ECMO anticoagulation and additional study of novel tests are needed to identify and avoid clinical complications. Disclosures Tarasev: Functional Fluidics:Current Employment, Current equity holder in private company.Hines:Functional Fluidics:Current equity holder in private company.Chitlur:Biovertiv:Honoraria;Pfizer:Honoraria;Novo Nordisk:Consultancy, Honoraria;Takeda:Honoraria;Agios Pharmaceuticals:Research Funding.

Introduction Acute Promyelocytic Leukemia (APL) prognosis has largely improved over the past decades and is now the acute leukemia with the highest cure rates. However, its early death rate, which reaches 30% in several real-world studies, is the main obstacle to achieving lifelong remission in most patients. Several reports have suggested a potential role of the Disseminated Intravascular Coagulation (DIC) Score of the International Society of Thrombosis and Hemostasis as a marker of bleeding and death in APL. Since the APL-induced coagulopathy and hyperfibrinolysis are responsible for most early deaths, a method to assess the severity of the coagulopathy could guide the daily patient management and the intensity of the blood products used. We aimed to test the hypothesis of whether the improvement of the DIC Score through coagulopathy support can improve the rate of early death in APL. Methods This retrospective, single-center study, included consecutively admitted patients with newly diagnosed genetically confirmed Acute Promyelocytic Leukemia between 2000 and 2020, who were treated with ATRA + anthracycline protocols and prednisolone 0.5 mg/kg differentiation syndrome prophylaxis. All patients received platelets, fibrinogen, and/or fresh frozen plasma according to published clinical indications. Baseline demographics and clinical data were collected, and the DIC Score was calculated at diagnosis and after 48 hours for each patient, using fibrinogen, platelets, prothrombin time and d-dimers. "DIC Score improvement" was defined as an increase of ≥1 point in the calculated score at 48 hours; a stable or decreasing score were considered "no-improvement". A 30-day follow-up for each patient was conducted, and any death during this period was considered in the early-death group. Statistical analysis was performed using Stata, with chi-square test and Mann-Whitney test for differences between groups, and logistic regression for the analysis of predictors of early death. Results A total of 67 patients were included, after excluding 9 patients for missing coagulation values, 8 for first-line arsenic trioxide treatment, and 7 patients for death within 48 hours of hospital admission. The median age was 53 years (25-82), and 29.9% of patients were aged >60 years old. The 30-day mortality rate for this cohort was 31.3%. Comparing the baseline differences between the two groups, the only statistically significant difference detected was a less frequent improvement of the DIC Score over 48 hours in the early-death group (42.86% versus 76.09% in the remaining patients, p=0.008). There was no difference in the Sanz Risk distribution nor age between the two groups. The univariate analysis of predictors of death in 30 days (logistic regression) yielded age >60 years and 48h-improvement of the DIC Score as potential predictors of death. A multivariate analysis model was built incorporating these 2 variables with the Sanz Risk (the number of events in this study permitted only a 3-variable prognostic model), and it identified age>60 years (OR 4.84 [1.37-17.10]; p=0.014) and the lack of a 48-hour improvement in the DIC Score (OR 5.46 [1.61-18.47]; p=0.006) as independent predictors of early death. In patients under 60 years old, having no improvement in the DIC Score over 48 hours is still associated with almost five times superior odds of 30-day mortality (OR 4.55; p=0.038). Conclusion In this cohort, we identified a lack of DIC Score improvement and age>60 years as independent predictive factors of early death in APL. These findings identified a new independent predictor of early death using a dynamic DIC Score assessment, which is easily accessible and calculated, and illustrate how this score can be applied daily in the clinical care of APL patients. Together with the current APL treatment strategies, the intensification of measures to control the leukemia-associated coagulopathy in patients who do not show a DIC Score improvement in the first 48 hours after diagnosis could decrease the early death rate in this otherwise highly-curable leukemia. Disclosures Brioso Infante: Astellas: Speakers Bureau; Novartis: Speakers Bureau.

Tigecycline, a first representative of the new class of glycylcycline antibacterial drugs, has been approved by FDA for using in the treatment of complicated skin and skin structure infections and community-acquired pneumonia in adults in 2005. It has been widely used in hospitals due to its broad-spectrum activity against pathogens. Pre-clinical studies showed that tigecycline has a significant anti-bacterial effect with low and mild adverse drug reactions (ADRs), including nausea, vomit or some other ADRs. Accompany with the huge increase of tigecycline usage in China, more and more side effects began to arouse people's attention. Here, we found that tigecycline can cause coagulation abnormalities in cancer patients, especially with hematological malignance, through clinical observation and retrospective analysis. To analyze the effect and risk factors of tigecycline on coagulation index in severely infected patients with hematologic cancer, we screened the cases admitted to department of hematology from three hospitals treated with tigecycline from Nov, 2015 to Oct, 2019. Then we compared the differences among the prothrombin time (PT), prothrombin time activity (PT %), the international standardization ratio (INR), part of the activation of prothrombin time (APTT), fibrinogen (FBG), thrombin time (TT), D-Dimer, fibrin degradation products (FDP), platelet (PLT), alanine aminotransferase (ALT), aspartate aminotransferase (AST), creatinine (CRE), and c-reactive protein (CRP) before and after the tigecycline treatment. Meanwhile, we tend to establish the relationship between coagulation function and the time of tigecycline usage. In addition, for exploring the potential cause of abnormal coagulation induced by tigecycline, we evaluated the underlying biological mechanisms via Chinese hamster ovary (CHO) cells treated by tigecycline in vitro and subsequent RNA-sequencing analysis. A total of 129 qualified cases were included for analysis, including 71 males (55%) and 58 females (45%), with average age of 49.5±15.9 years old. After the treatment with tigecycline, PT, APTT and TT were significantly prolonged (P < 0.05). The INR, D-Dimer and FDP levels also increased (P < 0.05), but the FBG concentration was significantly reduced (P < 0.05) which indicated the possibility of hypofibrinogenaemia. Moreover, the coagulation parameters were tremendously changed in the early stage after intravenous infusion of tigecycline for anti-infection. There was no significant change in PLT count, but the levels of ALT, AST, CRE and CRP in the patients were statistically significant declined (P < 0.05). Most of all, the liver and kidney function of the patients was recovered after the infection was controlled by tigecycline treatment. In addition, the adhesion and stretching function of CHO cells were significantly suppressed after tigecycline treatmentin vitro. Lastly, bulk RNA-sequencing assay showed significant abnormalities in gene sets associated with platelet-activation and coagulation, such as PKFP, PLA2g7, PDGFRA, PDGFRB, PAFAH1b3, PDGFA, PECAM1, PDGFC and MPIG6b. Furthermore, adhesion regulating molecules RPN13, CHL1, ICAM5, TLCN were also downregulated by tigecycline treatment. What's more, these key genes which showed above need to be further validated in blood samples of AML patients when treated with tigecycline. Taken together, tigecycline can cause coagulation disorders in blood cancer patients. As we known, blood cancer could disturb the normal hematopoietic reconstitution in bone marrow, which resulted in abnormal numbers and functions of the peripheral blood lineages. Hence, these ADRs can accelerate the disease progression, cause severe bleeding and increase the risk of mortality in these patients. The biological mechanism study of this abnormality showed that tigecycline could inhibit platelet activation and the expression of adhesion regulators, which may increase the risk of bleeding and threaten the safety of patients. Therefore, the monitoring of coagulation index during tigecycline treatment should be adopted. Disclosures No relevant conflicts of interest to declare.

JAK2V617F-positive essential thrombocythemia is rarely associated with mutation in the thrombomodulin gene and deficiency of protein S without being reported in the literature. A case of a previously healthy 50-year-old Chinese female presenting with superior mesenteric vein thrombosis and portal thrombosis showed by enhanced computed tomography(CT) scan is reported. Blood platelet count showed 644×109/L. Molecular testing for genetic mutation found a JAK2V617F mutation by 11089 copies per 100ng DNA revealed by real-time polymerase chain reaction (RT-PCR), with the mutation rate being over ten percent. Level of free protein S decreased to 30.4%(reference:70%-140%). Heterozygous missense mutation(c.404C>G, i.e.nucleotide 404 of encoding region was mutated from cytosine to guanine) in exon 1 in the thrombomodulin gene was detected in peripheral blood, which caused p.Pro135Arg(i.e.amino acid No.135 was changed from proline to arginine). The chromosomal position of thrombomodulin gene was at chr20:23029738. Family investigation showed that a similar mutation in the thrombomodulin gene was detected in peripheral blood in her daughter. Low molecular weight heparin was given at the beginning of treatment, and bleeding was monitored. In the meantime, warfarin was administered orally and the dosage of which was adjusted to maintain the international normalized ratio of prothrombin time at the range of 2 to 3. Adjust the dosage of hydroxyurea according to blood cell count. A month later, no new thrombosis was found in enhanced CT scan. It was an amazing feat that the patient was in a state of remission without new thrombosis being found for a year. JAK2V617F-positive essential thrombocythemia with mutation in the thrombomodulin gene and deficiency of protein S tends to be incurable. Warfarin alone with hydroxyurea may serve as an effective option to those cases. Disclosures No relevant conflicts of interest to declare.

Central venous catheter thrombosis can cause venous obstruction and pulmonary embolism. To determine the extent to which catheter thrombosis is triggered by the contact or extrinsic pathway of coagulation, we used antisense oligonucleotides (ASOs) to selectively knock down factor (f)XII, fXI, or high-molecular-weight kininogen (HK), key components of the contact pathway, or fVII, which is essential for the extrinsic pathway. Knockdown of contact pathway components prolonged the activated partial thromboplastin time and decreased target protein activity levels by over 90%, whereas fVII knockdown prolonged the prothrombin time and reduced fVII activity to a similar extent. Using a rabbit model of catheter thrombosis, catheters implanted in the jugular vein were assessed daily until they occluded, up to a maximum of 35 days. Compared with control, fXII and fXI ASO treatment prolonged the time to catheter occlusion by 2.2- and 2.3-fold, respectively. In contrast, both HK and fVII knockdown did not significantly prolong the time to occlusion, and dual treatment with fVII- and fXI-directed ASOs produced a time to occlusion similar to that with the fXI ASO alone. These findings suggest that catheter thrombosis is triggered via the contact pathway and identify fXII and fXI as potential targets to attenuate this complication.

Background : Double filtration plasmapheresis (DFPP) is a form of therapeutic plasma exchange (TPE) that removes high-molecular-weight (HMW) pathological mediators from the plasma with two filters: a plasma separator and a plasma fractionator. Relative to simple TPE, the semi-selectiveness of DFPP reduces protein loss and the need for substitution fluid. However, depending on the choice of plasma fractionator, DFPP may negatively impact hemostatic components such as HMW coagulation factors. Aim: To determine the impact of DFPP on various hemostatic parameters (i.e. FVIII activity, fibrinogen level, vWF level and activity, ADAMTS13 level and activity, protein C (PC) activity, protein S (PS) activity, antithrombin (AT) activity, prothrombin time (PT), and activated partial thromboplastin time (aPTT)). Methods: Fourteen patients undergoing weekly, bimonthly, or monthly DFPP sessions for hematologic conditions (n=11) or nervous system disorders (n=3) were recruited. Hemostatic parameters were measured immediately before and after 27 DFPP sessions (1-4 sessions/patient). The treatment volume was standardized at one plasma volume, and anticoagulation was performed with ACD-A citrate dextrose solution. EC-30W and EC-50W were used as the plasma fractionators in 4 and 23 sessions, respectively. In addition to primary data collection, we systematically searched PubMed, MEDLINE, and EMBASE for studies that investigated the impact of DFPP on hemostasis. No restriction was placed on filter choice. Results: In our cohort of 14 patients, all hemostatic changes were statistically significant. After a routine DFPP session, the level and/or activity of HMW proteins (>100kDa: FVIII, fibrinogen, vWF, ADAMTS13) were decreased more than those of low-molecular-weight (LMW) proteins ( Our systematic review included 26 cohort studies, 6 case reports, and 1 randomized controlled trial. Increases in INR and aPTT following DFPP were considerably higher in previous studies, which may relate to the commonality of heparin-induced anticoagulation. The present study is the first comprehensive investigation of the impact of DFPP on hemostatic parameters with such a large sample size. It is also the first study of its nature to measure ADAMTS13-related parameters. Conclusions: Routine DFPP resulted in significant reduction across all investigated hemostatic proteins and significant prolongation of clotting tests. The activities of HMW coagulation-related proteins were decreased more than those of LMW anticoagulation-related proteins. This finding suggests that DFPP may increase overall bleeding risk, a consideration for patient safety that may be of importance in continuous DFPP treatment. Additional high quality evidence is needed to elucidate the effect of DFPP on the hemostatic system. Disclosures Matino: Sanofi: Honoraria; Sobi: Honoraria, Research Funding; Roche: Research Funding; Bayer: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding; Bioviiix: Honoraria.

Background: Coagulation has notoriously been a topic that medical trainees find challenging to learn. A lack of understanding around coagulation has led to widespread inappropriate ordering of commonly used coagulation tests, including the prothrombin time (PT) and the activated partial thromboplastin time (aPTT). Despite these tests being validated for specific clinical indications, they are frequently ordered as screening tests in unselected patients, and often ordered together, suggesting a gap in physician understanding of coagulation and appropriate testing. To explore this further, we conducted a root-cause-analysis survey of 10 medical trainees. 70% of the surveyed trainees did not feel comfortable with their knowledge regarding coagulation and the appropriate use of coagulation tests. Trainees attributed their suboptimal knowledge to the manner in which coagulation is taught in training programs. Furthermore, they identified a scarcity of practical resources on coagulation and expressed interest in a web-accessible resource. Methods: We created an educational module on coagulation testing for trainees, available online at www.coagtesting.com. This module was created with the intent of simplifying the teaching of coagulation, with a focus on emphasizing clinically-relevant concepts. The module was evaluated at the University of Toronto with 50 participating medical trainees (11 medical students, 39 internal medicine residents [14 PGY1, 15 PGY2, 10 PGY3 residents]). Participation in our study included completing a validated knowledge pre-quiz on coagulation, completion of the educational module, and then the post-quiz following the module. To assess longer term knowledge retention, participants were asked to repeat the knowledge quiz three months following their initial participation. Our educational intervention was evaluated according to the Kirkpatrick Model, a framework for learning evaluation, with educational outcomes organized into four ranked levels (level 1, reaction; level 2, learning; level 3, behaviour; level 4, results). The primary objective of this study was to determine if the module improves trainee knowledge of coagulation, as indicated by their quiz results (level 2, learning). The secondary objective was to evaluate if the module has an influence on trainee ordering practices as assessed by a follow-up survey (level 3, behaviour). Results: The median pre-module quiz score was 67% (range 24% - 86%) with an increase of 24% to a median post-module quiz score of 91% (range 64% - 100%). Notably, in the pre-module quiz, 94% of trainees overestimated the sensitivity and specificity of the PT and aPTT in detecting a bleeding disorder, and 44% of trainees underestimated the cost of a PT test. 80% of trainees described increased confidence regarding their knowledge of coagulation and the use of coagulation tests following completion of the module. In addition, we have demonstrated sustained knowledge acquisition with a 3-month post-quiz median score of 89% (n=15, range 67%-100%). 100% of trainees who completed the 3-month follow-up survey (n=15) felt that the educational module had a positive influence on their practice and 87% of trainees were more likely to consider the sensitivity, specificity, and cost of a lab test prior to ordering it. In the seven months since the module was launched, it has been completed by over 2,000 unique visitors worldwide, with use in Canada, the United States, the United Kingdom, Australia, France, and Saudi Arabia according to data from our website host. Furthermore, several visitors to the website have re-visited the module multiple times. Conclusion: We have successfully demonstrated a significant increase in trainee knowledge and confidence regarding coagulation and appropriate use of coagulation tests with our educational intervention. Using the expertise of medical educators and incorporating feedback from trainees, we have employed a novel approach to the teaching of coagulation to maximize its approachability and clinical relevance. Our module also incorporates education on the cost of coagulation testing and appropriate use of these tests thus in line with the tenets of Choosing Wisely. The degree to which trainees have been utilizing and re-referring to our educational module worldwide emphasizes the need for this resource and its importance in bridging a large gap in medical training. Disclosures Sholzberg: Novartis: Honoraria; Amgen: Honoraria, Research Funding.

Factor V Leiden (FVL) is an incompletely penetrant thrombosis susceptibility variant common in humans. This incomplete penetrance suggests there are modifiers of FVL (F5L) that alter the susceptibility to a thrombotic event. To identify modifiers, we performed a sensitized ethylnitrosourea (ENU) mutagenesis screen in mice to induce mutations suppressing the F5L/LTfpi+/- perinatal lethal thrombotic phenotype. Although we identified thrombosuppressor mutations in two of our 22 independent MF5L mouse lines thus far, the others are still unknown. Our mouse line MF5L16 has produced a large, highly penetrant (77.2%), multigenerational pedigree containing 136 viable F5L/LTfpi+/- mice. We performed the Prothrombin Time (PT) assay on plasma from a subset of these mice and observed a significantly longer PT in MF5L16F5L/LTfpi+/- mice compared to F5+/LTfpi+/- and Tfpi+/- control mice (q Disclosures No relevant conflicts of interest to declare.

Introduction: The incidence of venous thrombotic event (VTE ) after lung tansplantation was recently evaluated to approximately 44 % in a large series of patients (Neto et al., Transplantation. 2018; 102: 681). Cystic fibrosis (CF) is a devastating chronic inflammatory disease caused by a mutation in the gene encoding cystic fibrosis transmembrane regulator (CFTR), which is a chloride channel in epithelia cell membranes. Coagulation balance in patient with CF is complexed since there is both a decrease in vitamin K-dependent factor but also an excess of physiological inhibitors deficiencies. Lung fibrosis was also sometimes associated to a higher thrombotic risk. Aim: To analyse whether thrombin generation assay (TGA), which takes in account both pro-and anticoagulant factors, or the activity of soluble tissue factor (TFa) are able to discriminate the thrombotic risk of patients after bipulmonary lung transplantation (BLT) and are better discriminant than classical thrombophilia screening test [prothrombin time (PT), activated partial thromboplastin time (APTT), antithrombin (AT), protein C (PC) S (PS), Z (PZ) fibrinogen (FG) and FVIII levels (FVIIIc) measurements]. Methods: Thrombophilia screening (including TGT in the presence or absence of thrombomodulin (TM) and TFa quantification) was performed for 166 consecutive patients before BLT. Patients were divided in 3 categories : 100 with CF, 43 with chronic obstructive pulmonary disease (COPD) and 23 with idiopathic pulmonary fibrosis (IPF). Among them, 91 (51 with CF, 28 with COPD and 12 with IF) were transplanted. Proven VTE (positive duplex ultrasound) during the first trimester was registered. Results: Because of a defect in lipophilic vitamin absorption, prothrombin time below 70 % and a significant higher proportion of PZ deficiency was observed in patients with CF, in comparison to COPD. The frequency of AT, PC and PS were not significantly different between the 3 groups of patients. Because the chronic pulmonary contamination of the lung by bacteria, the frequency of elevated fibrinogen levels were significantly higher in patients with CF as compared to COPD and IPF groups (table 1). Median TFa values were significantly higher (p < 0.05) in patients with CF (median 0.24 pg/mL, range 0.1 - 7.7) than in patients with COPD (median 0.1 pg/ml, range 0.1 - 0.63). FTa was also elevated (median 0.24, range 0.1 - 6.15) in patients with IPF. Time to Peak (tt-Peak) was significantly shorter in patients with CF as compared to COPD or IPF, even in the presence of thrombomodulin (TM). MRI were higher in patients with CF than in patients with COPD or IPF, even in the presence of TM. Peak was higher in patients with CF as compared to patients with COPD (p < 0.05). In the presence of TM, Endogenous prothrombin potential (ETP) was significantly higher in patients with CF as compared to patients with COPD, and the ratio ETP/ETP with TM was higher in patients with CF as compared to patients with COPD or IPF, indicating a defective PC pathway in patients with CF (table 2). Among the 91 patients with BLT, a VTE was evidenced in 25 (27.5%) patients, with a similar frequency between the 3 groups (33.3 % in CF, 14.7 in COPD, 33.3 % in IPF, not significant). We analysed separately patients with CF from patients with COPD or IPF, since there were differences between coagulation parameters tested in patients with CF. Only APTT ratio was significantly lower (p < 0.01) in patients with CF who had a VTE (1.04) than in patients without VTE (1.12). No difference in the different parameters tested was evidenced in patients with COPD and IPF Conclusion: Even if TGA and TFa clearly evidence a more prothrombotic phenotype in patients with CF than in patients with COPD or IPF, thrombophilia screening before BLT fail to identify patients with a high post-operative thrombotic risk. Disclosures No relevant conflicts of interest to declare.

Background: Acute heavy menstrual bleeding (HMB) is common for adolescent females, with about a quarter of menstruating females seeking care for HMB over a 3-year time period (O'Brien et al, Blood 2018). Inherited bleeding disorders are common in this adolescent population, identified in 24.6% referred for hematologic evaluation (Zia et al, Blood 2016). The timing and contents of the hemostatic workup for acute HMB in adolescents is extrapolated from adults, although the causes of acute HMB varies significantly between adult women and adolescents. A consensus statement by the American College of Obstetrics and Gynecology recommends obtaining a variety of hemostatic tests including CBC, von Willebrand studies, factor VIII, prothrombin time, partial thromboplastin time, fibrinogen, and thyroid stimulating hormone at the time of presentation (Committee Opinion 557, ACOG 2011). Factor VIII and Von Willebrand studies are known to be increased in the setting of physiologic stress and supplemental estrogen use, questioning their diagnostic accuracy in the setting of acute bleeding. Repeat testing is often required for diagnosis of von Willebrand disease A von Willebrand factor antigen (VWF:Ag) or von Willebrand factor ristocetin cofactor level over 100IU/dL has been shown to have a negative predictive value (NPV) of 95%.(Doshi et al, ASH 2018). Methods: As part of a quality improvement initiative to improve the evaluation and management of adolescents with HMB at Children's Healthcare of Atlanta (CHOA), we instituted an acute HMB protocol for emergency department (ED) and inpatient use. This protocol was implemented at all CHOA emergency departments in metropolitan Atlanta. Subjects were included if they presented with acute HMB as determined by an adapted Philip Menorrhagia Screening Tool. Subjects with a previously diagnosed bleeding disorder, ITP, active rheumatologic disease, cancer, or anticoagulant use were excluded. Descriptive statistics were used to summarize demographics and clinical characteristics. Patients with a positive Philip screen underwent a uniform bleeding inventory and a standardized set of laboratory tests based on the adult consensus statement. Inpatient and outpatient treatments were standardized by hemoglobin level and symptomology. Follow up with hematology and gynecology was encouraged for all. Data was extracted using various heavy menstrual bleeding ICD-10 codes from January 1, 2017 to December 31, 2018. Individuals with von Willebrand studies at baseline and follow up were identified. T-tests and Wilcoxon rank sum tests were utilized to compare VWF:Ag, VWF:RCo and Factor VIII as baseline and follow up. Results: Over a 2-year period, 232 adolescent girls were seen in CHOA EDs for acute HMB with 88 (37.9%) requiring admission and 6 (2.6%) requiring intensive care. The population was primarily African American (63%) with a median age at presentation of 14.8 years (IQR 13.1-16.7). The majority of adolescents had the core hemostatic labs drawn (55.6%) as described per protocol. Thirty-six individuals had baseline and follow up VWD studies. Those with repeat VWD studies were younger (median 13.2 years vs 15.0 years), more commonly white (44.4% vs 21.2%), were more likely to have been admitted (83.3% vs 29.6%) and more likely to have had a hematology follow up appointment (63.4% vs 7.8%). Mean and median VWF:Ag, VWF:RCo and Factor VIII were significantly higher at presentation with HMB than at follow up. Of those with a baseline VWF:Ag and/or VWF:RCo >100, there was a 96.4% NPV for the diagnosis of VWD. For individuals whose initial VWF:Ag and VCWF:RCo were both >100, there was 100% NPV. Conclusions: Among the adolescents cared for at our institution with acute HMB who had confirmatory VWD testing, initial VWF:Ag and VWF:RCo >100 ruled out VWD based on repeat testing. However, poor adherence with hematology or gynecology follow-up may give false reassurance against a diagnosis of VWD. Further improvements of our quality improvement initiative will include a limited hemostatic workup at presentation with a focus on improved adherence to follow up and subsequent hemostatic evaluation. Disclosures White: National Hemophilia Foundation: Other: Shire Clinical Fellowship Program. Sidonio:Kedrion: Research Funding; Novo Nordisk: Membership on an entity's Board of Directors or advisory committees; Takeda-Shire: Membership on an entity's Board of Directors or advisory committees, Research Funding; Bioverativ: Membership on an entity's Board of Directors or advisory committees, Research Funding; Genetech: Membership on an entity's Board of Directors or advisory committees, Research Funding; Octapharma: Membership on an entity's Board of Directors or advisory committees, Research Funding; Grifols: Membership on an entity's Board of Directors or advisory committees, Research Funding; Biomarin: Membership on an entity's Board of Directors or advisory committees; Uniqure: Membership on an entity's Board of Directors or advisory committees.

Introduction: Skin eruptions in acute myeloid leukemia (AML) patients are not uncommon. Skin biopsy is a minimal invasive procedure, yet potential complications, such as infection and bleeding, might be expected in these patients due to immunosuppression and thrombocytopenia. Data are scarce regarding the prevalence, etiology and characteristics of skin eruptions among AML patients during intensive therapies. Even less is known regarding the safety and diagnostic yield of skin biopsies in this setting. We sought to evaluate the diagnostic yield and safety of skin biopsies obtained from adult AML patients during hospitalization for intensive chemotherapy. Methods: This is a single-center retrospective cohort study of adult AML patients who underwent skin biopsies for histopathology and tissue culture during induction and consolidation treatment for AML at our hemato-oncology unit between 1.1.2007-1.9.2018. Data collection included demographic details, AML characteristics, chemotherapy regimens, clinical description of rush and associated symptoms (mainly fever, pruritus) and laboratory tests. We recorded whether biopsy results had an impact on patients' care. This study was approved by the Institutional Review Board. Results: 37 skin biopsies from AML patients were identified in our cohort during the study period. Patient demographics and rash characteristics are presented in Table 1. 22% of the skin biopsies were performed at AML presentation prior to chemotherapy, and the remainder after chemotherapy commencement, i.e. after starting either induction or post-induction (consolidation or salvage) treatment (70% and 8%, respectively). Most skin eruptions were grade 1 (53%) or 2 (26%) in severity. Only 21% were grade 3 and 4 rashes. The most common body parts involved were the limbs (51%) and trunk (33%). At the time of skin biopsy 43% of patients had associated fever and 11% had bacteremia. Most patients (62%) had grade 4 neutropenia and 38% and 19% of patients had grade 3 and 4 thrombocytopenia, respectively. Elevated prothrombin time was evident in 66% of patients, whereas 5.5% of patients had an elevated partial thromboplastin time at the time of biopsy. Rash etiology according to skin biopsies histopathological findings consistent with drug eruptions (24.3%), infections (11%), leukemia cutis (16.2%), Sweet syndrome (5.5%) or a reactive process (8%). 35% of biopsies results were inconclusive. In 16 cases (43%) tissue cultures were performed and of those, 4 cultures were positive. However, only in 1 patient the positive culture result has led to a change of antimicrobial coverage. A proactive approach following biopsy results was conducted in 2 additional patients, when a suspected drug leading to the eruption was discontinued (n=1), and systemic steroids were prescribed instead of acyclovir (n=1). Hence, skin biopsy results changed patients' management only in 8% of cases (n=3). Skin biopsies were generally safe and only 1 patient suffered from a complication directly attributed to the biopsy - i.e. she became febrile and suffered from a local hemorrhagic bulla formation, necessitating administration of vancomycin. Conclusions: We suggest that skin biopsies from AML patients hospitalized for intensive chemotherapy treatment are relatively safe. Nevertheless, their diagnostic yield is limited and does not alter the management of most patients. Increased physician discretion should be exercised prior to performing a skin biopsy in this patient population, to avoid unnecessary usage of medical resources and invasive procedures. Further studies are needed to establish the role of skin biopsies in these patients. Disclosures Wolach: Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Speaker; AbbVie: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Speaker.

Introduction: The metabolic syndrome is a complex disorder characterized by the presence of a clustering of metabolic risk factors usually in a single individual associated with the presence of central obesity and a strong association with diabetes and cardiovascular disease morbidity and mortality. It is a fast spreading global pandemic & emerging as a public health problem with poor outcome and Quality of life thus more predilection is towards preventive than curative treatment. According to WHO Clinical Criteria, Metabolic syndrome is defined as insulin resistance, identified by 1 of the following, Type 2 diabetes, fasting blood glucose more than 110 mg/dl plus any 2 of the following: antihypertensive medication and /or high blood pressure > 140 mm systolic or >90 mm diastolic, plasma triglyceride (TG) level more than 150 mg/dl (1.7 mmol/L), high-density lipoprotein (HDL) cholesterol level less than 35 mg/dl (0.9 mmol/L) in men or less than 39 (1.0 mmol/L)in women , BMI >30 kg/m2 and/or waist:hip ratio >0.9 in men, > 0.85 in women, Urinary albumen excretion rate > 20 mcg/min or albumin:creatinine ratio>30mg/g Aims & Objectives: To investigate the coagulation profile derangements in metabolic syndrome. To study the relationship of various components of metabolic syndrome with coagulation parameters. Material & Methods: This was a prospective cross-sectional study carried out in Haematology & Medicine Deptt of SafdarJang Hospital, New Delhi. After taking consent from the Hospital Ethics Committee, a total of 50 cases of metabolic syndrome presenting as outpatient or inpatient were included in the study. 50 age & sex matched controls were selected which did not satisfy the criteria for metabolic syndrome. Observation & Results: In our study we found that the cases with metabolic syndrome have significantly increased levels of Fibrinogen, Factor VIII and Plasminogen Activator Inhibitor1 (PAI1). PT & APTT were shorter in cases with metabolic syndrome. The mean value of fibrinogen in cases was 402.24 ± 66.92 mg/dl while that in control was 261.5 ± 41.95 mg/dl with a P value of The mean value of Factor VIII in cases was 152.66 ± 7.54 IU/dl while that in control was 131.44 ± 6.24 IU/dl with a P value of The mean value of Plasminogen Activator Inhibitor1 (PAI1) in cases was 49.99 ± 5.34 ng/ml while that in control was 36.75 ± 3.35 ng/ml with a P value of Prothrombin Time (PT) values in cases were 9.79 ± 0.74 seconds and in controls were 12.04 ± 0.7 seconds & this difference was statistically significant (p Activated partial Thromboplastin Time (APTT) values in cases were 28.96 ± 0.92 seconds and in controls were 32.6 ± 1.34 seconds & this difference was statistically significant (p Conclusions: The coagulation parameters studied correlated significantly with the components of metabolic syndrome. The values varied significantly with increased number of features of metabolic syndrome. Thus we can conclude that metabolic syndrome is a hypercoagulable state and further studies are required for further evaluation of the consequences of this hypercoagulable state.. Disclosures No relevant conflicts of interest to declare.

Background: The concept of developmental hemostasis has been universally accepted. Plasma concentrations of many coagulation factors in childhood are significantly different from adults for both mean values and ranges of normal. Thus, an understanding of developmental hemostasis and the development of appropriate age-dependent reference ranges are pivotal for prevention, diagnosis, and treatment of hemostatic problems during childhood. However, no data of developmental hemostasis are available in healthy Chinese children. Methods: Coagulation data from children aged 0-18 years old receiving minor elective surgery in Chengdu Women and Children's Central Hospital, from Sep. 2017 to Feb. 2019 was collected, and patient medical records were reviewed. Ethical approval was obtained from the parents of all children and the study was approved by the Ethics Review Committee at Chengdu Women and Children's Central Hospital. To qualify for the study, enrolled subjects had to meet the following criteria: (1) Children aged 0-18 years receiving minor elective surgery.(2) No history of bleeding problems.(3)No family history of bleeding nor thrombosis .(4) No history of heart, lung, liver or kidney diseases, normal physical examination. (5) Normal blood routine test. Normal liver function and kidney function, (6)No history of medication use for at least two weeks prior to specimen collection.(7) The operation gone successfully, and postoperative recovery was well. Blood samples (3 mL) were obtained by venipuncture into plastic tube containing 3.2% (109 mmol/L) buffered sodium citrate (1 part citrate:9 parts blood). The specimens were centrifuged immediately at 2500 g for 15 min at room temperature to prepare platelet-poor plasma (PPP) for the preoperative coagulation screening tests, consisting of activated partial thromboplastin time (APTT), prothrombin time (PT)), international normalized ratio (INR), thrombin time (TT) and fibrinogen. Activity of coagulation factors VIII, IX, XI, XII,Ⅱ,Ⅴ,Ⅶ,Ⅹ were determined using one-stage clotting methods with respective factor-deficient plasma. Results: A total of 82 samples were collected, while only 67 met the enrollment criteria. Specimens with inappropriate ratio of blood to anticoagulant, hemolysis or abnormal values of coagulation tests (APTT, PT, TT, fibrinogen) were excluded from analysis. The total of 67 children (40 Male 27 female), with a median age of 2.0 years (range: 1month -14 years) were divided into three groups according to the age: 6y group 7cases. (1) The values of APTT, PT, TT, and fibrinogen were (36.1±5.2) seconds, (11.1±0.85) seconds, (20.3±1.6) seconds, (2.4±0.89) g/L respectively. No significant differences were found between groups. (2) In all children ,the activities of factor VIII、IX、XI、XII、vWF、II、V、VII、X were(123.6±48.3)%、(75.9±16.9)%、(95.9±24.3)%、(43.7±16.3)%、(111.3±50.4)%、(90.2±14.0)%、(104.7±21.1)%、(81.6±19.1)%、(93.0±21.8)% respectively. Factor VIII and vWF activities were significantly higher than other factors, while factor XII activities were significantly lower than others. (3)Mean values of FII:C, FVIII:C, FIX:C, FXI:C were significantly lower in children below Conclusions: Coagulation test is just a simple and easy screening test. Coagulation factor activities changed dynamically with age during childhood, especially the FII:C, FVIII:C, FIX:C and FXI:C. Physiological reference ranges for coagulation factor activities in Chinese children of different ages should be established in order to evaluate the children with congenital or acquired bleeding diseases correctively. Table Disclosures No relevant conflicts of interest to declare.

Background: Patients with acute myeloid leukemia (AML) presenting with hyperleukocytosis have frequent complications and early mortality. Pulmonary, central nervous system, and cardiovascular complications are common. Attempts to improve outcomes in the 10% of AML patients arriving with hyperleukocytosis have included leukapheresis. No prospective randomized study has supported the use of leukapheresis, and retrospective reports have revealed persistently poor outcomes as well as emerging concerns of acquired coagulopathy and worsening hypoxemia after leukapheresis. While many centers use a leukapheresis protocol processing two blood volumes, Johns Hopkins protocol routinely processes three-five blood volumes. This study aimed to assess coagulopathy, hypoxemia, and mortality with large volume leukapheresis. Methods: 32 patients with newly diagnosed AML treated with large volume leukapheresis for WBC depletion are included in this report. Demographic, clinical, laboratory, and apheresis-related data were collected. Coagulopathy and hypoxemia-related metrics were evaluated within 6 hours before leukapheresis and within 6 hours of completion of leukapheresis. Descriptive and inferential statistics (chi square and Mann-Whitney U test) were used to compare pre and post-leukapheresis findings and assess clinical outcomes. Results: Twenty-nine of 32 (93.8%) patients presented with symptomatic leukostasis (with pulmonary and/or CNS symptoms in 26/29). Median blood volume processed was 14.8 liters (range 4-23.4L). Mean platelet count decreased from 60x109/L to 37x109/L after leukapheresis (p Conclusions: Patients with AML presenting with hyperleukocytosis have a very high mortality, particularly when complicated by symptomatic leukostasis. Similar to Van de Louw's report, we observed worsening coagulopathy and a subgroup with increased oxygen requirements after leukapheresis. While our sample size is too small to draw broad conclusions, we were not able to identify a group clearly benefiting from leukapheresis. We did not find evidence that larger volume leukapheresis decreased complications or mortality. These results should lead to caution when considering leukapheresis for patients with newly diagnosed AML, particularly in those presenting with a severe coagulopathy. Table Disclosures Webster: Pfizer: Consultancy; Amgen: Consultancy; Genentech: Research Funding. Gojo:Amphivena: Research Funding; Amgen Inc: Consultancy, Honoraria, Research Funding; Juno: Research Funding; Merck: Research Funding; Jazz: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Abbvie: Consultancy, Honoraria. Pratz:Boston Biomedical: Consultancy; Millenium/Takeda: Research Funding; Agios: Consultancy, Research Funding; Astellas Pharma: Consultancy, Research Funding; AbbVie: Consultancy, Research Funding. Smith:Celgene: Consultancy; Jazz: Consultancy; Pfizer: Consultancy; Agios: Consultancy; Novartis: Consultancy. DeZern:Astex Pharmaceuticals, Inc.: Consultancy; Celgene: Consultancy. Levis:Amgen: Consultancy, Honoraria; Agios: Consultancy, Honoraria; Astellas: Consultancy, Research Funding; FUJIFILM: Consultancy, Research Funding; Menarini: Consultancy, Honoraria; Novartis: Consultancy, Research Funding; Daiichi Sankyo Inc: Consultancy, Honoraria.

Introduction: Currently there are four commercially available oral anti-Xa agents namely apixaban, betrixaban, edoxaban and rivaroxaban available for indication specific clinical use. All agents used are at a fixed dosage and their use may be associated with potential hemorrhagic complications. Although factor Xa inhibitory effect is considered to be a surrogate marker for the biologic action of these drugs we have demonstrated that factor Xa inhibitory profile of apixaban, betrixaban, edoxaban, and rivaroxaban does not fully reflect their biologic spectrum (https://doi.org/10.1177/1076029619847524). Furthermore the prothrombin time (PT) and activated partial thromboplatin time (aPTT) methods are of limited sensitivity and are dependant on several other enodogenous factors. Prothrombinase induced clotting time (PiCT), (Pentaharm, Basel, Switzerland) is a sensitive test for the global monitoring of anticoagulant drugs including heparins and parenteral oral anti-Xa and anti-IIa agents. The test is based on the RVV venom activation of endogenous FVa which forms prothrombinase complex with phospholipids (PL), FXa and calcium. The clot-based end point is proportional to the activities of FXa and FIIa. This study is designed to compare the relative responses of PT, aPTT and PiCT test in normal human blood, retrieved plasma and agents supplemented plasma with the oral anti-Xa agents to demonstrate the relative sensitivity of this assay in comparison to the PT and aPTT. Materials and Methods: Active pharmaceutical ingredient versions of apixaban, betrixaban, edoxaban and rivaroxaban were obtained from commercial sources. All agents were prepared at a stock concentration of 100ug/ml in saline and diluted to a working solution of 10ug/ml. Serial dilutions were prepared in various matrices. Citrated plasma from normal individuals (n=50) was obtained from a commercial source (George King Biomedical, Overland Park, Kansas). Whole blood and plasma samples (n=20) were supplemented at a concentration of 0-1000 ng/ml. Whole blood samples were also centrifuged to obtain retrieved plasma. These samples were analyzed using a single stage PiCT, aPTT and PT. Whole blood and retrieved plasma studies were carried out by using ST4 (Diagnostica Stago). PiCT were measured by using Pefakit PiCT. aPTT measurements were made by using Tcoag, TriniCLOT aPTT (Diagnostica Stago, Paris, France). For PT, HemosIL TM (Instrumentation Laboratory, MA, USA) was used. All results were compiled in individual groups as mean + SD. Results: All of these drugs produced a concentration dependent anticoagulant effects in the PiCT, aPTT and PT tests in both the whole blood and plasma systems. PiCT consistently showed much higher sensitivity in comparison to other tests. When compared at 1000ng/ml the anticoagulant effects of these drugs were stronger in plasma systems as shown in the table. PiCT consistently showed higher sensitivity in comparison to PT and aPTT in the whole blood, retrieved plasma and agent supplemented plasma. Edoxaban showed the strongest anticoagulant activity measured by PiCT in comparison to the other agents. Matrix based variations in the PiCT results were observed. Interestingly, the retrieved plasma from whole blood showed weaker anticoagulant effects in comparison to the directly supplemented plasma systems. Discussion: In comparison to PT and aPTT, the PiCT test was found to be the most sensitive in the three matrices studied. In the whole blood and plasma-based systems PiCT test showed linearity and high sensitivity for all of the four anti-Xa agents. In the PiCT test, consistently drug supplemented plasma showed the highest response in comparison to retrieved plasma and whole blood, suggesting differential binding of these drugs to cells. These results indicate that the PiCT test can be reliably used for the monitoring of anti-Xa agents. PiCT test can also be performed on currently available optical and mechanical instrument used for clotting studies. Owing to rapid turnaround time, high sensitivity, and lower cost PiCT can be used for the routine monitoring of oral anti-Xa agents. Table Disclosures Tafur: Recovery Force: Consultancy; Janssen: Other: Educational Grants, Research Funding; BMS: Research Funding; Idorsia: Research Funding; Daichi Sanyo: Research Funding; Stago: Research Funding; Doasense: Research Funding.

A 3-1/2-year-old male with no personal or family history of bleeding disorders presented with abdominal distension, epistaxis, and anemia (hemoglobin 8.2 g/dL). A magnetic resonance imaging scan of the abdomen demonstrated a mass arising from the left kidney. Preoperative laboratory studies revealed a prolonged activated partial thromboplastin time of 49.2 seconds, a normal prothrombin time of 12.4 seconds, and a platelet count of 230 000/μL. Further testing revealed factor VIII (FVIII) activity of 16%, factor IX (FIX) activity of 74%, von Willebrand factor (VWF) activity of 12%, VWF antigen activity of 31%, and decreased high-molecular-weight VWF multimers consistent with acquired von Willebrand syndrome (AVWS). What is the best treatment for this child?

Perinatal stroke causes cerebral palsy and lifelong disability. Specific diseases are definable, but mechanisms are poorly understood. Evidence suggests possible associations between arterial perinatal stroke and prothrombotic disorders, but population-based, controlled, disease-specific studies are limited. Understanding thrombophilia in perinatal stroke informs pathogenesis models and clinical management. We conducted a population-based, prospective, case-control study to determine the association of specific perinatal stroke diseases with known thrombophilias. Children with idiopathic magnetic resonance imaging-classified neonatal arterial ischemic stroke (NAIS), arterial presumed perinatal ischemic stroke (APPIS), or fetal periventricular venous infarction (PVI) were recruited. Standardized thrombophilia evaluations were performed after 12 months of age on stroke cases and controls, including quantified proteins C and S, antithrombin, factors VIII/IX/XI, fibrinogen, lipoprotein(a), homocysteine, lupus anticoagulant, anticardiolipin antibodies and genotyping of factor V Leiden (FVL), factor II G20210A (FII), and methylenetetrahydrofolate reductase C677T. A total of 212 children were studied: 46 with NAIS, 34 with APPIS, 55 with PVI, and 77 controls (male, 53%; median age, 4.8 years). Of 14 parameters, no differences were observed in 12, including all common thrombophilias. Mean prothrombin time was shorter in arterial strokes (P < .001). Rates of antiphospholipid antibodies were low, comparable to those in controls, and resolved on repeat testing. FVL and FII rates were comparable to population norms. Total number of possible abnormalities did not differ between cases and controls. Our prospective, population-based, controlled, disease-specific study suggests minimal association between perinatal stroke and thrombophilia. This does not exclude the possibility of disordered coagulation at the time of stroke but suggests testing in childhood is not indicated.

Introduction: The prothrombin time (PT) and partial thromboplastin time (PTT) are often considered 'routine' tests in the outpatient setting. They are frequently used as screening tests for bleeding disorders in unselected patients despite sensitivities ranging of 1-2 %. For the most common bleeding disorder, a negative score on a bleeding assessment tool (BAT), in the presence of a negative family history, has a NPV of 1. A recent quality improvement study conducted in the emergency department at our institution resulted in a greater than 2-fold reduction in coagulation test ordering rates and more than $6000 CAN direct cost-savings per month. Objectives: We developed a multimodal sequential quality improvement study in the outpatient family practice unit with the primary aim of minimizing unnecessary coagulation testing and maximizing the appropriate use of a BAT. Materials and Methods: We have developed four interventions using plan-do-study-act (PDSA) cycles to achieve our goal. Cycle (1) baseline assessment of ordering rates, involved stakeholder engagement, development of educational tools and addition of the BAT onto the electronic medical record (EMR). Cycle (2) involved assessment of EMR-available BAT. Cycle (3) involved an audit to determine appropriateness of coagulation testing for patients on oral anticoagulants and a subsequent targeted intervention. Cycle (4) involved alteration of the laboratory requisition and facilitating access to decision support and educational materials. Rates were calculated per 100 patient visits per month. Data were analyzed on Strata 13 using an interrupted time series analysis. Results: After Cycle 1, we saw a significant decrease in rates of PT and PTT ordering from 1.9 tests per 100 patient visits per month (for both tests) to 1.5 and 1.4 respectively; (p< 0.001 for both). However, the rate of creatinine (control) testing rate also decreased significantly (8.9 to 8; p=0.006). With Cycle 2, we found that all referrals for bleeding from the family practice unit were appropriate and only 19% of patients who had a BAT completed were referred. In Cycle 3, we identified an inappropriate PT and PTT ordering rate of 11% and 36% respectively for patients on oral anticoagulants. We also identified that PT and PTT were being tested together despite being ordered individually; further investigation revealed that they were being erroneously coupled by laboratory technicians. Finally, results of Cycle 4 showed no significant change in INR (increase by 0.05; p=0.64) or PTT (increase by 0.01; p=0.95) testing rates but a significant increase in control testing rates (0.68; p=0.016) in the first 4 months after the intervention. Conclusions: From our previous quality improvement project in the emergency department, we learned that educational interventions alone are often not sufficient and that a process change is required to achieve meaningful change in coagulation test utilization. Through EMR integration of the BAT we successfully guided hematology referrals for bleeding. We were unable to alter rates of PTT testing despite physically removing the PTT from the lab requisition. This likely reflects the strength of the cultural link between INR and PTT. Planning is underway for PDSA Cycle 5 which will consist of a lab audit of PTT testing and subsequent targeted intervention. Disclosures James: Shire: Research Funding; Bayer: Research Funding; CSL Behring: Research Funding.

Background: In hemophilia patients with inhibitors, hemostasis can be achieved using bypass agents: activated plasma-derived prothrombin complex concentrates (aPCC), recombinant Factor VIIa (FVIIa), or emicizumab - that can only manage hemophilia A. Marzeptacog alfa (activated) (MarzAA), an engineered recombinant FVIIa with enhanced biological properties enabling subcutaneous (SQ) delivery was developed using a rational protein design approach. It has 7-fold increased catalytic activity and prolonged duration of effect demonstrated in a single-dose intravenous (IV) study that documented safety. Daily SQ dosing in dogs demonstrated achievement of stable trough levels of MarzAA that are believed to be effective for prophylaxis. Aims: Phase 2/3 Study MAA-201 (NTC03407651) will determine if SQ MarzAA can provide effective prophylaxis. This study complies with the Declaration of Helsinki and is approved by recognized research ethics committees. Up to 12 subjects with inhibitors, who have an annualized bleeding rate ≥12 (ABR), and sign informed consent, will participate. Methods: After an 18 mg/kg MarzAA IV bolus, pharmacokinetics and coagulation parameters were measured for 24 hours followed by 30 mg/kg MarzAA SQ with pharmacokinetics and coagulation parameters measured for a further 48 hours to calculate bioavailability. Subjects then received daily 30 mg/kg MarzAA SQ for 50 days. If no spontaneous bleeding events occurred the subject proceeded to safety follow-up 3 weeks after the last dose. If spontaneous bleeding occurred, dose escalation occurred sequentially to 60, 90 or 120 mg/kg for 50 daily doses as needed (fig 1). Subjects were monitored for treatment-related changes in Quality of Life measures and tested for anti-drug antibodies to MarzAA and FVII weekly. ABR was compared to the subjects prior ABR. Results: 5 participants have been enrolled (Median ABR 16.6; Range 12.2-26.7) (fig 2). One participant with historical ABR 26.7 has completed the study with no bleeding at 60 mg/kg MarzAA but had a spontaneous bleed 16 days into the follow-up period when no longer receiving study drug. In a participant with previously-treated but currently-untreated and uncontrolled hypertension, a fatal hemorrhagic stroke deemed unrelated to study drug occurred on Day 11. Pharmacokinetics are shown in fig 3. IV half-life of 3.5 hours was increased to SQ half-life of 9.5 hours. Levels of MarzAA at Tmax 5 hours after SQ injection were similar to levels at 6 hours after IV infusion. Median subcutaneous bioavailability was 35%; Range 32.4-37.5%. Prothrombin Time baseline of 12-12.7 seconds fell to 8-9 seconds after 18 µg/kg IV infusion (normal 9.4-12.5 seconds). Prothrombin Time gradually declined to 8.7 seconds after 7 days of 30 µg/kg SQ injection. No anti-drug antibodies have been detected to date. Conclusion: This study demonstrates that an individualized dose of daily SQ MarzAA can provide effective prophylaxis in hemophilia patients with inhibitors. Supported by Catalyst Biosciences Disclosures Levy: Catalyst Biosciences: Employment, Equity Ownership. Mahlangu:Sanofi: Research Funding, Speakers Bureau; Roche: Consultancy, Research Funding, Speakers Bureau; LFB: Consultancy; NovoNordisk: Consultancy, Research Funding, Speakers Bureau; CSL Behring: Consultancy, Research Funding, Speakers Bureau; Chugai: Consultancy; Catalyst Biosciences: Consultancy, Research Funding; Biomarin: Research Funding, Speakers Bureau; Biogen: Research Funding, Speakers Bureau; Bayer: Research Funding; Amgen: Consultancy; Alnylam: Consultancy, Research Funding, Speakers Bureau; Shire: Consultancy, Research Funding, Speakers Bureau; Sobi: Research Funding, Speakers Bureau; Spark: Consultancy, Research Funding. Del Greco:Catalyst Biosciences: Employment, Equity Ownership. Booth:Catalyst Biosciences: Consultancy.

Introduction: We previously demonstrated Black patients with acute myeloid leukemia (AML) are more likely to require ICU-level resources at initial presentation. This disparity in acuity at presentation explained 62% of the two-fold racial disparity in early mortality (Winestone Am J Hematol 2017). We sought to expand these findings using a more detailed data source that leverages electronic medical record (EMR) data from two large institutions. We hypothesized that disparities in severity at presentation by race, ethnicity, and socioeconomic status would be identified in granular EMR data for children with acute lymphoblastic leukemia (ALL) and AML. Methods: Acute leukemia patients who were diagnosed at Children's Hospital of Philadelphia or Texas Children's Hospital (2006-2014) were included. Patients who transferred from a referring hospital or whose race was specified as Asian, other, or unknown were excluded. Race and ethnicity were combined into 3 mutually exclusive categories: Hispanic, non-Hispanic White, and non-Hispanic Black. The first set of vital signs (blood pressure, heart rate, respiratory rate, and temperature) and the timing of key diagnostic evaluations were manually abstracted. Patient age, sex, race/ethnicity, residential address, and results of selected laboratory tests from the first 72 hours after admission underwent automated extraction from the EMR. Residential addresses were batch-matched to geo-coordinates linking each patient to a census-derived block group. The following measures of socioeconomic status (SES) were evaluated: median household income, education, unemployment, and crowding. Vital signs were interpreted using age-specific American Heart Association reference ranges. Individual and composite lab-based definitions created a priori were used to identify high disease burden, risk of infection, renal dysfunction, abnormal coagulation (prothrombin time >17 or fibrinogen 200 or bilirubin >2.5 or GGT>150). Log-binomial regression was used to compute unadjusted prevalence ratios (PR) and corresponding 95% confidence intervals (CI) comparing incidence of vital sign and laboratory abnormalities by race/ethnicity and block group SES. Stratification by leukemia type (AML vs. ALL) allowed for assessment of heterogeneity in associations of interest. Covariates that were associated with race and thus were potential confounders were also included in multivariable models to obtain adjusted PRs. Results: A total of 899 acute leukemia patients (474 non-Hispanic White, 318 Hispanic, and 107 non-Hispanic Black) were included. Figure 1 shows patient characteristics including patients' geo-coordinates mapped onto census block group median household income. Vital signs at presentation were generally similar across racial/ethnic groups with the exception of heart rate among Hispanic patients (62% vs. 53%, p=0.03). Black patients with AML had an increased prevalence of elevated white blood cell (WBC) count and uric acid and Black patients with ALL demonstrated increased prevalence of coagulopathy compared to White non-Hispanic patients (Table 1). For both AML and ALL, Black patients were more likely to have more than 2 lab abnormalities relative to White non-Hispanic patients. There were no clinically significant differences in time to key diagnostic evaluations by race/ethnicity; median time to CBC was under 2 hours for all racial/ethnic groups, median times to bone marrow biopsy and lumbar puncture ranged from 25-39 hours, and median time to chemotherapy was between 2-3 days. None of the measures of SES were significantly associated with abnormal vital signs, abnormal labs, or prolonged time to key diagnostic evaluations. Conclusions: Black patients with newly diagnosed AML present with increased prevalence of high disease burden as evidenced by elevated WBC and uric acid. Across acute leukemia types, Black patients are more likely to present with more than 2 lab abnormalities; these lab abnormalities likely represent physiologic dysfunction at diagnosis and may compound one another to explain the previously observed racial disparity in ICU-level care requirement. Similar ethnic differences were not observed among Hispanic patients with AML or ALL. We are conducting ongoing investigation into the impact that rurality and distance to the hospital have on initial presentation. Disclosures Fisher: Merck: Research Funding; Pfizer: Research Funding.

Background: Prothrombin time (PT) and activated partial thromboplastin time (aPTT) are screening tests of hemostasis commonly ordered for anticoagulant therapy monitoring, evaluation of bleeding, screening for acquired or inherited deficiencies of coagulation factors, and preoperative screening. Evaluation of a prolonged PT/aPTT is best accomplished in an algorithmic fashion consisting of mixing studies and factors assays or inhibitor testing as indicated. However, there is little data available on frequency of conditions that may result in abnormalities of PT/aPTT. The Special Coagulation Laboratory (SCL) at our institution offers an algorithmic approach termed Prolonged PT/aPTT Profile (PT/aPTT profile). Aim: To review our institutional experience with PT/aPTT profile testing (indications and outcomes), and to provide clinical correlation of abnormal PT/aPTT tests on patients seen at our institution in an effort to explain common causes of altered hemostatic testing in outpatient clinical practice. Methods: In this retrospective study, following IRB approval, we reviewed the medical records of patients who underwent outpatient PT/aPTT profile testing in the SCL at Mayo Clinic in Rochester, Minnesota between 2010 and 2017. Data abstracted included patient demographics and clinical presentation, indications for testing, use of anticoagulants, medical diagnoses which could potentially influence coagulation, and results of hemostatic testing (Table 1). Statistical analyses were completed using SAS 9.4 (SAS Institute Inc., Cary, North Carolina). Continuous variables are presented as median (range) while discrete variables are summarized as frequency (percentage). Comparisons of clinical characteristics between groups are made using the rank-sum test for continuous variables. Statistical significance is defined as a 2-tailed P value of less than 0.05. Results: A total of 107 patients met our study criteria, 58 (54 %) male, median age 55 years (range 1-89). Indications for testing included prior prolongation of PT (48%), PTT (29%), PT and aPTT (8%) on outside coagulation testing performed in a non-SCL setting, clinical bleeding episodes (10%) and preoperative screening (5%). Patients with established medical diagnoses known to influence coagulation testing including solid tumors, hematologic malignancies, liver disease, renal disease, autoimmune and rheumatologic conditions and pregnancy were documented along with other baseline patient characteristics (Table 1). SCL PT/aPTT profile testing revealed normal results in 29 of 107 (27%) patients on repeat testing while 78 patients warranted further evaluation of which 27 (35%) had an isolated prolonged PT, 28 (36%) had a prolonged APTT and 23 (29%) had prolongations of both PT and aPTT. After further workup and clinical correlation, causes of abnormal outpatient PT/aPTT profile testing were found to be related to an underlying congenital condition in 16 (21%) patients - most commonly factor VII deficiency (9%) and factor VIII deficiency (4%) - acquired conditions in 53 (68%) patients - most commonly anticoagulant therapy effects (31%) and liver disease (21%) - and of unclear etiology in 7 (9%) cases (Table 2). Specifically, the most common cause of an isolated prolonged PT in our study was found to be vitamin K deficiency (37%) whereas elevations in aPTT and both PT/aPTT were most frequently attributed to the effects of anticoagulant therapy (29% and 52% respectively). Other causes of prolongation on PT/aPTT profile testing following clinical correlation were also identified (Table 2). Discussion: While PT and aPTT are commonly ordered tests, there is little evidence regarding epidemiology of testing indications, distribution of test results, and the clinical correlation of test results. Our study demonstrates that abnormalities in hemostatic testing can be attributed to a wide range of causes including artefactual prolongation influenced by pretest variables or marked abnormalities in secondary hemostasis due to inherited and acquired conditions. Strengths of this study include the SCL algorithmic approach to testing to further elucidate coagulation cascade abnormalities to properly characterize conditions that pose severe hemostatic risk while limitations of this study reflect the experience of a single institution and possible referral bias. Disclosures No relevant conflicts of interest to declare.

Background: Traditional prothrombin time (PT) based international normalized ratio (INR) is often highly variable. Often this is caused by rapid factor VII reductions due to its short (4 hour) half-life. Thus, factor VII variation is an important confounder during vitamin K antagonist (VKA) dosing. Furthermore, prior studies have demonstrated that factor VII reductions only minimally influence the antithrombotic effect and bleeding risk of VKA, the clinical effect depending mainly on controlled reduction of factors II and X. Therefore, ignoring the influence of FVII during VKA monitoring has the potential to simplify management and outcome. The Fiix prothrombin time (Fiix-PT) is a new modified PT that is only affected by reduced factors II and X. The Fiix-PT is not affected by variations in factor VII. Hence, the Fiix normalized ratio (Fiix-NR) fluctuates less than the standard standard PT-INR. In the double-blind randomized clinical Fiix-trial, published in 2015, monitoring of warfarin with with Fiix-PT (Fiix-NR) was compared to standard high time-in-range PT-INR monitoring. Fiix-NR monitoring led to improved time-in-range, reduced testing frequency, reduced dose-adjustment need and a 50% reduction in thromboembolism (TE). Bleeding did not increase and it occurred at a low rate in both trial arms. Subsequently starting on July 1st 2015 we replaced the PT-INR with Fiix-NR in our anticoagulation monitoring practice. Aim: We compared anticoagulation outcome and dosing frequency during 12 months prior to switching from PT-INR based management (Pre-Fiix monitoring period) and during 12 months following switch to Fiix-NR monitoring (Fiix monitoring period). Methods: This is a retrospective before and after study involving unselected patients managed at a single anticoagulation management service at the Landspitali University Hospital in Reykjavik, Iceland. All patients on warfarin during two consecutive twelve month periods were analysed irrespective of indication or anticoagulation target range. Pre-Fiix patients analysis was based on events occuring during months -12 to -1 before replacing the PT with Fiix PT and the Fiix patients´outcome was analysed during months +4 to +15. Three transitional months were excluded. All patients were dosed by specialized staff using the DAWN anticoagulation software®. Hospital chart diagnostic codes were reviewed for occurrence of TE or major bleeding (MB) during the two separate monitoring periods.Surrogate assessments included the number of tests, testing intervals and dose adjustment frequencies and will be analyzed later. Results: During the Pre-Fiix period 2,345 patients were managed with PT-INR for 1,984 patient years (0.85 years/patient) and during the Fiix period 1,909 patients were managed with Fiix-NR for 1,643 patient years (0.86 y/pt). Indications for warfarin were identical during both periods (atrial fibrillation 57%, venous thromboembolism 26%, prosthetic heart valves 5% and other 12%). The INR target range during both periods was 2.0-3.0 in 92% and 2.5-3.5 in 6%. Clinical outcome with respect to TE and MB is shown in the figure. Overall the point estimates were suggestive of a 34-52% reduction of TE with Fiix-NR monitoring whereas major bleeding was similar. The reduction in untoward events in the Fiix group was statistically significant for composite new TE (OR 0.63;0.41-0.97) and total stroke (ischemic and hemorrhagic, OR 0.57;CI 0.33-0.98), mainly driven by reduced cerebral infarction. Intracranial bleeding occurred in 0.76% in the Pre-Fiix group and in 0.37% in the Fiix montoring group (n.s., OR 0.51;0.19-1.32). The median time-within-Target-range (TTR, Rosendaal method) was similar in both groups (75 vs 76%, respectively), despite dose adjustment frequency being reduced by 18% in the Fiix monitoring group (OR 0.82;CI 0.79-0.85, p Conclusions: These results are in agreement with the results of the Fiix-trial and show that ignoring factor VII during VKA monitoring is safe and leads to reduction in thromboembolism without increasing bleeding. Although TTR was identical in both groups, the dose adjustment need was reduced possibly indicating that less anticoagulation variability in the Fiix-NR group explains reduced thromboembolism. Figure Figure. Disclosures Gudmundsdottir: Hart Biologicals Ltd: Consultancy, Patents & Royalties: Hart Biologicals Ltd is commercializing the Fiix-PT which will be ready for marketing in Europe in the beginning of year 2019 and possibly later that year in the USA. Patent fees will be paid to Fiix Diagnostics Ltd once the test is commercialized.; Fiix Diagnostics Ltd: Equity Ownership, Patents & Royalties: The Fiix prothrombin time (Fiix-PT) is a patented invention of P. T. Onundarson and B.R. Gudmundsdottir that is owned by Fiix Diagnostics Ltd, a start-up company founded by the inventors. . Onundarson:Hart Biologicals Ltd: Consultancy, Other: Hart Biologicals Ltd is commercializing the Fiix-PT which will be ready for marketing in Europe in the beginning of year 2019 and possibly later that year in the USA. Patent fees will be paid to Fiix Diagnostics Ltd once the test is commercialized.; Fiix Diagnostics Ltd: Equity Ownership, Patents & Royalties: The Fiix prothrombin time (Fiix-PT) is a patented invention of P. T. Onundarson and B.R. Gudmundsdottir that is owned by Fiix Diagnostics Ltd, a start-up company founded by the inventors. .

Introduction: There are four oral anti-Xa drugs currently available for clinical use in various indications. These drugs are claimed to mediate their therapeutic effects by solely targeting factor Xa. While these agents are structurally similar, their biochemical properties and their effects on blood coagulation differ. Such differences may impact their safety and efficacy profile. The purpose of this study was to demonstrate the differences among factor Xa inhibitors in terms of their in vitro anticoagulant activity and other biochemical effects. Materials and Methods: Commercially obtained powdered forms of Apixaban, Betrixaban, Edoxaban and Rivaroxaban were profiled in this study. Stock solutions of each drug were prepared at 1mg/ml. To investigate the effect on the whole blood clotting profile, thromboelastographic studies were carried out over a concentration range of 0.5 - 2.5 ug/ml and whole blood activated clotting time (ACT) was measured at 1.0 and 2.5 ug/ml. The anticoagulant profile in citrated human pool plasma was measured at concentrations of 0.062-1.0 ug/ml using such tests as prothrombin time (PT) and activated partial thromboplastin time (aPTT). The anti-Xa effects of each agent were measured using a kinetic amydolytic method. The inhibitory potency was calculated in terms of IC-50. Thrombin generation inhibition studies on each drug were carried out in human pool plasma in a concentration range of 0.0-1.0 ug/ml using calibrated aotomated thrombogram (CAT) assay (Diagnostica Stago, Paris, France). Fibrinokinetics studies were carried out using an optical kinetic method, where thrombin was used to trigger clot formation. All results were compiled in terms of mean + 1 SD of 3-5 replicates. Results: All of the anti-Xa agents produced concentration and assay-dependent effects in these studies. The summary of each agent's effects at selected fixed concentrations and the IC-50 of the anti-Xa activity is given in the Table. In the whole blood ACT at 2.5ug/ml, Edoxaban showed the strongest anti-coagulant effects followed by Rivaroxaban > Betrixaban, whereas Apixaban showed minimal effects. In the TEG analysis at 1ug/ml, Edoxaban exhibited stronger anti-coagulant effects as measured by various TEG parameters, including R-time, K-time, alpha, and MA. Edoxaban and Rivaroxaban showed comparable effects followed by Betrixaban, whereas Apixaban exhibited weaker effects. In the PT assay at 1ug/ml, Edoxaban showed stronger effects, whereas Apixaban, Betrixaban and Rivaroxaban were comparable. aPTT at 1ug/ml revealed that Edoxaban was the strongest anti-Xa inhibitor followed by Betrixaban, whereas Apixaban and Rivaroxaban were comparable. In the anti-Xa assay Edoxaban was stronger (IC-50 = 340ng/ml, 0.62uM) than Apixaban (IC-50 =400ng, 0.87uM), Rivaroxaban (IC-50 = 840ng, 1.9uM) and Betrixaban (IC = >1000ng, >2.22 uM). In the thrombin generation assays at 1ug/ml, Apixaban showed the strongest inhibitory activity (IC-50 = 50ng/ml, 108nm) followed by Edoxaban (IC-50 = 58ng/ml, 108nm), Betrixaban (IC-50 = 60ngml, 133nm) while Rivaroxaban showed relatively weaker activity (IC-50 = 100ng/ml, 299nm). In the fibrinokinetics study at 1ug/ml, the anti-Xa agents produced varying degrees of inhibition with Rivaroxaban (67%), Edoxaban (42%), Apixaban (32%) and Betrixaban (12%). Summary and Conclusion: These results demonstrate that the measured anti-Xa activity alone does not fully reflect the overall biologic spectrum of these agents. Assay dependent variations are exhibited by each of these drugs, revealing distinct individual profiles. Edoxaban was the only anti-Xa agent which consistently exhibited relatively stronger inhibitory profile which was proportional to its anti-Xa activity. These studies indicate that the oral anti-Xa drugs may modulate the hemostatic system through additional mechanisms independent of the inhibition of factor Xa. Table. Table. Disclosures No relevant conflicts of interest to declare.

Background: Increased thrombin generation in vivo is pivotal to the development of disseminated intravascular coagulation (DIC). Typically, thrombin is generated when the prothrombinase complex, composed of activated factor X (FXa), activated co-factor V (FVa) and phospholipids, cleaves prothrombin in the presence of calcium. In critical illness, extensive cell death releases histones into the circulation, which can increase thrombin generation. However, the underlying pathophysiological mechanisms remains to be fully elucidated. Methods: In vitro: Isolation of histone-binding proteins with mass spectrometry analysis. Surface plasmon resonance binding studies, prothrombin cleavage and thrombin generation assays. In vivo: histone infusion mouse models (C57BL/6 mice) with or without prothrombin fragment F1+F2 infusion. Clinical: a prospective cohort of 129 adult intensive care unit patients (ICU) with sepsis and analysed for DIC. Results: Histone-conjugated Sepharose beads were used to pull down proteins from human plasma. Histone-binding proteins were subjected to 2D gel electrophoresis and sequenced by liquid chromatography-mass spectrometry. Prothrombin was the only coagulation factor identified. Histones directly bind to prothrombin (H3 [Kd = 6.8 x 107 M] and H4 [Kd = 7.0 x 107 M]), specifically prothrombin fragments F1+F2, to facilitate FXa-induced prothrombin cleavage and thrombin generation (H4 [12.25 ± 1.25 fold] and H3 [8.82 ± 0.67 fold]). FXa levels are the limiting factor of histone-enhanced thrombin generation since this process was inhibited in FX-deficient plasma unless exogenous FXa was added. Specifically, using either heparin or anti-histone antibodies to block histones, histone-prothrombin interactions, prothrombin cleavage and subsequent thrombin generation were significantly reduced. Unlike FVa which requires a phospholipid surface to form functional prothrombinase complexes, histones can substitute for FVa in the absence of phospholipids. The addition of histones to FV-deficient plasma restored thrombin generation, suggesting that histones can bypass FVa to induce thrombin generation. In vivo, infusion of histones into mice caused significant decreases in platelet counts and fibrinogen levels with elevations in thrombin-antithrombin complexes, D-dimer and prothrombin time in a dose-dependent manner. Pathological examination indicated intravascular thrombi with various organs, particularly in within lung tissues. These histone-induced DIC changes were significantly abrogated when prothrombin fragments F1+F2 were infused prior to histones to act as a decoy for binding of histones to circulating prothrombin. Analysis of DIC scores in ICU patients (n=129) with sepsis showed circulating histone levels to strongly correlate with DIC scores (r=0.446, p Conclusions: Histones can replace FVa in prothrombinase and not require phospholipid surfaces. This alternative histone-assembled prothrombinase can explain how thrombin could be generated and amplified away from cell surfaces to cause systemic dissemination of its effects and potentiate DIC. This study also identifies circulating histones as a potential target for therapeutic intervention in reducing DIC development and subsequent multi-organ failure in ICU patients. Disclosures No relevant conflicts of interest to declare.

Continuous expression of activated factor VII (FVIIa) via gene transfer is a potential therapeutic approach for hemophilia patients with or without inhibitory antibodies to human factor VIII (FVIII) or IX (FIX). Here, we investigate whether gene transfer of an engineered canine FVIIa (cFVIIa) transgene can affect hemostasis in a canine model of hemophilia, a good predictor of efficacy of hemophilia treatments. Purified recombinant cFVIIa exhibited 12-fold higher tissue factor–dependent activity than purified recombinant zymogen cFVII. Subsequently, we generated a serotype 8 recombinant adeno-associated viral vector expressing cFVIIa from a liver-specific promoter. Vector delivery via the portal vein in hemophilia A and B dogs was well tolerated, and long-term expression of cFVIIa resulted in a shortening of the prothrombin time, partial correction of the whole blood clotting time and thromboelastography parameters, and a complete absence of spontaneous bleeding episodes. No evidence of hepatotoxicity, thrombotic complications, or inhibitory immune response was found. These data provide the first evidence for in vivo efficacy and safety of continuously expressed FVIIa as a FVIII/FIX-bypassing agent in a large animal model of hemophilia, avoiding the risk of inhibitor formation associated with bolus FVIII or FIX infusion.

Introduction: Rivaroxaban is an oral, direct Factor Xa (FXa) inhibitor in advanced clinical development for the prevention and treatment of thromboembolic disorders, including arterial indications such as acute coronary syndromes (ACS). The aim of this study was to determine whether rivaroxaban can prevent arterial thrombotic occlusion in electrolytically injured rat carotid arteries. Methods: Anesthetized, male Sprague-Dawley rats were equipped with an intravenous (i.v.) catheter to administer drug or vehicle and an intra-arterial catheter for arterial pressure monitoring and blood sampling. The left carotid artery was exposed and a bipolar electrode placed proximally around it. A pulsed Doppler flow probe was then placed distally around the vessel. Blood was obtained before drug or vehicle administration to determine activated clotting time (ACT), prothrombin time (PT), Russell’s viper venom time (RVVT), activated partial thromboplastin time (aPTT) and thrombin-antithrombin (TAT) complex concentration; baseline carotid blood flow was recorded for 20 minutes. Vehicle (polyethylene glycol:ethanol:water or saline, 0.5 mL/kg/min), rivaroxaban (0.3, 1 and 3 mg/kg; dosing volume 0.5 mL/kg/min), or the low molecular weight heparin enoxaparin (10 mg/kg) were infused i.v. over 30 seconds. After infusion, direct current (3 mA) was applied to the left carotid artery for 5 minutes. Blood flow was monitored for 30 minutes after injury. Blood was sampled again 14.5 and 30 minutes after injury for ACT determination, and after 30 minutes for PT, RVVT, TAT and aPTT determination. Results: Rivaroxaban dose-dependently increased the median time to arterial thrombotic occlusion (TTO), and was significantly more effective than vehicle at doses of 1 and 3 mg/kg (vehicle, 13.2 minutes; rivaroxaban 1 and 3 mg/kg, >30 minutes; P Conclusions: Rivaroxaban potently inhibited electrolytically induced arterial thrombotic occlusion in rat carotid arteries, resulting in substantial changes in coagulation parameters. The coagulation parameter changes were consistent with inhibition of FXa activity as indexed by the RVVT. These findings suggest that rivaroxaban may be an effective anticoagulant in arterial thrombotic disorders, such as ACS.

An ex vivo photochemical treatment (PCT) process was developed to inactivate pathogens in fresh frozen plasma (PCT-FFP). A prospective, controlled, double-blinded, randomized study was conducted to evaluate the efficacy and safety of PCT-FFP compared with conventional FFP (C-FFP). Patients (n = 121) with acquired coagulopathy, largely due to liver disease, including hepatic transplantation, were transfused with either PCT-FFP or C-FFP for up to 7 days. Primary end points were changes in the prothrombin time (PT) and the partial thromboplastin time (PTT) in response to the first FFP transfusion. Secondary analyses compared changes in the PT and the PTT, factor VII levels, clinical hemostasis, blood component usage, and safety following FFP transfusions for up to 7 days. Following the first transfusion, correction in the PT and PTT adjusted for FFP dose and patient weight was not different. Changes in the PT were equivalent between treatment groups (P = .002 by noninferiority). Equivalence was not demonstrated for changes in the PTT. Following multiple transfusions, correction of the PT and the PTT was similar between groups. No differences were observed in use of blood components, clinical hemostasis, or safety. These results suggest PCT-FFP supported hemostasis in the treatment of acquired coagulopathy similarly to conventional FFP.

Factor V (FV) deficiency, also known as parahemophilia, is a rare bleeding disorder. Herein we investigate the first reported missense mutation associated with FV deficiency, Ala221Val, assigned as FV New Brunswick. To elucidate the molecular pathology associated with the Ala221Val substitution, the mutation was recreated in a recombinant system together with 3 FV mutants (Ala221Gly, Glu275Gln, and Cys220Ala/Cys301Ala) designed to help explain the Ala221Val phenotype. The expression pattern was analyzed by pulse-chase experiments and an FV-specific enzyme-linked immunosorbent assay (ELISA), the results suggesting the Ala221Val mutation not to interfere with the synthesis or secretion. The functional properties of the recombinant FV New Brunswick were evaluated in both plasma clotting and purified systems. The Ala221Val mutation did not affect the factor Xa (FXa) cofactor function; nor did it interfere with the activated protein C (APC)–mediated down-regulation of activated FV (FVa) activity. However, FV New Brunswick demonstrated reduced stability at 37°C due to an increased rate of dissociation of light and heavy chains of FVa. In conclusion, this in vitro study of FV New Brunswick suggests the Ala221Val mutation not to impair synthesis and expression of procoagulant activity, indicating overall proper folding of the mutant molecule. Rather, the Ala221Val substitution appears to interfere with the stability of the activated FVa mutant, the reduced stability possibly explaining the deficiency symptoms associated with the mutation.

Severe deficiency of vitamin K–dependent proteins in patients not maintained on vitamin K antagonists is most commonly associated with poisoning by or surreptitious ingestion of warfarin, warfarin-like anticoagulants, or potent rodenticides (“superwarfarins”), such as brodifacoum. Serious bleeding manifestations are common. Superwarfarins are 2 orders of magnitude more potent than warfarin and have a half-life measured in weeks. These rodenticides are readily available household environmental hazards and are sometimes consumed accidentally or as manifestations of psychiatric disease. Immediate diagnosis and proper therapy is critically important to minimize morbidity and mortality because this condition, affecting thousands of patients annually, is reversible. Treatment with large doses of oral vitamin K1, often over months to years, to maintain a near-normal prothrombin time can reverse the coagulopathy associated with superwarfarins. Although these patients initially present to various medical specialties, the hematologist is often consulted to offer the definitive diagnosis and proper therapy.

Persistent postpartum hemorrhage is frequently complicated by coagulopathy even before the development of dilutional coagulopathy. If unnoticed, coagulopathy may contribute to massive unstoppable hemorrhage and ultimately death. Early assessment of coagulation status has been recommended to identify, and subsequently correct, coagulation abnormalities.2 Unfortunately, the turnaround times for the recommended standard tests (platelet count, prothrombin time, activated partial thromboplastin time, and fibrinogen concentration) are generally longer than 60 minutes, implying that by the time the results are available, the coagulation status may have changed considerably. Thus, rapidly available results of point-of-care tests, such as Fibtem, could significantly improve the outcome of women with postpartum hemorrhage. The findings of Collins et al show that Fibtem A5 measured after 1000 to 1500 mL postpartum hemorrhage was available 10 minutes after venipuncture and associated in a dose-response manner with progression to more severe hemorrhage.1 Given the perceived need for a faster test to diagnose coagulopathy in women with persistent postpartum hemorrhage, it is tempting to think that Fibtem should immediately be included in the series of tests for the assessment of coagulation status. However, there are several arguments against this notion. Fibtem results could improve clinical outcomes of women with persistent postpartum hemorrhage in 2 ways: first as a predictor of severe postpartum hemorrhage, and second as a diagnostic for coagulopathy. With respect to its role as a predictor, the Fibtem test is still in a preclinical phase. The successive phases of prognosis research are identification of the predictor, followed by development of a prediction model, external validation of the model, and finally assessment of the clinical impact of the model.3 Fibtem is now for the first time identified as predictor of severe postpartum hemorrhage1 and is therefore still in an early preclinical phase. The appropriate next step is the development of a multivariate prognostic model that combines relevant prognostic indicators, including primary cause of postpartum hemorrhage and other clinical characteristics. After validation, this model could serve to categorize women according to a low or a high risk for severe postpartum hemorrhage in order to be able to adjust treatment strategies accordingly. A second potential role for Fibtem in clinical practice would be to improve the timely diagnosis of coagulopathy. However, the clinical actions that follow the diagnosis of coagulopathy as assessed with Fibtem (possibly combined with other tests) have not been established. The results of the ongoing randomized trial studying whether fibrinogen concentrate can improve the outcome of women with moderate postpartum hemorrhage and low Fibtem values (ISRCTN46295339) will need to be awaited. Yet, even if fibrinogen concentrate is proven to be efficacious in women with low Fibtem values, we still don’t know whether the Fibtem with-or-without-fibrinogen-concentrate strategy is better (optimal cost-effectiveness) than other strategies. Besides the strategy of Fibtem measurement possibly followed by fibrinogen concentrate infusion, there is a myriad of other strategies to treat persistent postpartum hemorrhage. The strategies can be roughly categorized as laboratory driven and formula driven. In the laboratory-driven strategies, treatment decisions depend on laboratory parameters and treatment triggers to guide treatment decisions during persistent postpartum hemorrhage. The formula-driven strategies use a prearranged delivery system of (blood) products in various mixtures of products, such as tranexamic acid, red cells, plasma, platelets, and coagulation factors, to stabilize a hemorrhagic patient. These strategies have not been defined for postpartum hemorrhage, but it would be worthwhile to consider development of such a strategy. Coagulopathy and reduction in clotting factors can develop rapidly and soon after having a reassuring test result. With the formula-driven strategy, all women presenting with persistent postpartum hemorrhage can be treated without delay in a standardized way. The disadvantage of such a formula-driven strategy is that this strategy is not individualized and may therefore lead to both over- and undertreatment. The next sensible step would be to compare a well-designed, evidence-based, formula-driven strategy with a well-designed, evidence-based, point-of-care-test–driven strategy. The findings of Collins et al provide evidence in favor of Fibtem as a test in the laboratory-driven strategy. Particularly noteworthy in the report by Collins et al is the observation that in the multivariate model, fibrinogen is no longer associated with progression to severe postpartum hemorrhage, whereas Fibtem remains appreciably associated. This suggests that in these early phases of postpartum hemorrhage, other coagulation factors involved in clot formation, not fibrinogen concentration, might be more important for progression to severe postpartum hemorrhage. So an important question is, is fibrinogen at low normal concentrations causally related to progression to severe hemorrhage, or is it but an indicator of the severity and stage of the postpartum hemorrhage? An additional point that needs to be addressed is laboratory quality control. The TEG-Rotem working group reported large differences in test results among laboratories.4 Fibtem is a relatively costly commercial test, widely implemented in the thoracic surgery setting, and commercial forces are increasingly pushing its application in labor wards. Despite the promising results of Collins et al presented in this issue of Blood, we should bear in mind that new tests first need to undergo scrutinized testing for their clinical usefulness. Otherwise, implementation of this test might lead to needlessly high increases in health-care costs with insufficient gain or even loss in patient outcomes. Postpartum hemorrhage is common and potentially lethal. The study described by Collins et al1 provides promising findings with regards to the prediction of severe postpartum hemorrhage and early diagnosis of coagulopathy. A number of issues have to be addressed before implementation of Fibtem in the treatment strategy for women with ongoing postpartum hemorrhage. Thus, clinicians interested in Fibtem are encouraged to use the test in the framework of a well-designed scientific study.

The sequence of coagulant reactions in vivo following vascular injury is poorly characterized. Using quantitative immunoassays, the time courses were evaluated for activation of prothrombin, factor (F)V, FXIII, fibrinogen (Fbg) cleavage, and FVa inactivation in bleeding-time blood collected at 30-second intervals from 12 healthy subjects both before and after aspirin ingestion. Prothrombin decreased at a maximum rate of 14.2 ± 0.6 nM per second to 10% of initial values at the end of bleeding. Significant amounts of α-thrombin B chain appeared rapidly at 90 seconds of bleeding and increased at a maximum rate of 0.224 ± 0.03 nM per second to a peak value of 38 nM. Kinetics of prethrombin 2 generation was almost identical. Prothrombinase concentration reached a peak value of 22 pM at 150 seconds and then decreased to 9 pM at the end of bleeding. Prothrombin fragment 1.2 (F1.2) was produced explosively (0.673 ± 0.05 nM per second), whereas thrombin-antithrombin III (TAT) complexes were generated at a much slower rate (0.11 ± 0.008 nM per second;P = .002). FVa light chain was detectable 30 seconds later than the heavy chain (150 seconds) and was produced at a slightly slower rate (0.027 ± 0.001 nM per second) when compared with the heavy chain (0.032 ± 0.002 nM per second; P = .041). The 30 000 fragment (residues 307-506) of FVa heavy chain produced by activated protein C appeared as early as at 90 seconds and increased with time. Fbg was removed from the blood shed with a high rate of 0.047 ± 0.02 μM/s and became undetectable at approximately 180 seconds of bleeding. The velocity of FXIII activation correlated with thrombin B-chain formation. A 7-day aspirin administration (75 mg/d) resulted in significant reductions in maximum rates of (1) prothrombin removal (by 29%; P = .008); generation of α-thrombin B-chain (by 27.2%; P = .022), and prethrombin 2 (by 26%; P = .014); formation of F1.2 (by 31.4%;P = .009) and TAT (by 30.3%; P = 0.013); (2) release of FVa heavy chain (by 25%; P = .003) and FVa light chain (by 29.6%; P = .007); (3) Fbg depletion from solution (by 30.5%; P = .002); and (4) FXIII activation (by 28.6%; P = .003). Total amounts of the proteins studied, collected at every interval, also significantly decreased following aspirin ingestion. These results indicate that low-dose aspirin impairs thrombin generation and reactions catalyzed by this enzyme at the site of the injury.

To assess the relationship between venous thrombosis and plasma glucosylceramide (GlcCer) or phosphatidylethanolamine (PE), plasma levels of GlcCer and PE were determined for 70 venous thrombosis patients referred for evaluation and 70 healthy blood donors. The mean GlcCer level, but not the PE level, was lower in patients versus controls (4.9 vs 6.5 μg/mL [P = .0007] and 66 vs 71 μg/mL [P = .48], respectively). As a measure of relative risk, the odds ratio for deep vein thrombosis in subjects with GlcCer levels below the 10th percentile of controls was 5.7 (95% CI, 2.3-14). To assess the influence of glycolipids on anticoagulant response to activated protein C (APC):protein S in modified prothrombin time assays, the effects of depleting endogenous plasma GlcCer by glucocerebrosidase treatment or of adding exogenous purified GlcCer or other neutral glycolipids to plasma were tested. Glucocerebrosidase treatment reduced plasma sensitivity to APC:protein S in parallel with GlcCer reduction. Exogenously added GlcCer and the homologous Glc-containing globotriaosylceramide (Gb3Cer), but not galactosylceramide, dose-dependently prolonged clotting times of normal plasma in the presence, but not absence, of APC:protein S, which suggests that GlcCer or Gb3Cer can enhance protein C pathway anticoagulant activity. In studies using purified proteins, inactivation of factor Va by APC:protein S was enhanced by GlcCer alone and by GlcCer in multicomponent vesicles containing phosphatidylserine and phosphatidylcholine. These results suggest that the neutral glycolipids GlcCer and Gb3Cer may directly contribute to the anticoagulant activity of the protein C pathway and that deficiency of plasma GlcCer may be a risk factor for venous thrombosis.

Availability of platelets (plts) is severely limited by shelf life in some military as well as civilian settings. Additionally, some bleeding, thrombocytopenic patients do not have a therapeutic response to a standard plt transfusion. Methods for cryopreservation of apheresis plts for up to two years in 6% DMSO at Eligibility criteria were hospitalized thrombocytopenic hematology/oncology patients with active World Health Organization (WHO) Grade 2 or greater bleeding that was, in most patients, uncontrolled by standard plts, no history of unprovoked thrombotic events, and no indication of active DIC. Fifty-nine patients consented and 28 were transfused with ½ CPP unit (n=5), one CPP unit (n=7), two CPP units (n=6), and three CPP units (n=6). One thawed single apheresis CPP unit contained 2.5 x 1011 ± 4.2 x 1010 plts in 50 ± 4 ml. In addition, one standard apheresis plt unit was randomly given to patients enrolled in each cohort (n=4). The study conformed to the Declaration of Helsinki and was listed on clinical trials.gov (NCT02078284). Patients were monitored for six days post-transfusion for adverse events (AEs) including clinical assessments for signs or symptoms of thrombosis and specific laboratory assays: prothrombin time (PT), partial thromboplastin time (aPTT), D-dimer, fibrinogen, prothrombin fragments 1 + 2 (F1+2), antithrombin, thrombin antithrombin (TAT), thrombin generation (TGT), and thromboelastography (TEG). All safety data were reviewed by an independent data safety monitoring committee prior to escalation to the next higher dose cohort. No thrombotic events occurred after transfusion of CPP units. Five serious AEs were reported, and none were associated with the CPP transfusion but, rather, were related to worsening of the patients' underlying medical conditions. Of 38 AEs, 5 were, at least, possibly related to a CPP transfusion and included DMSO skin odor following a ½ CPP unit and three CPP units (n=2), mild fever and chills in the same patient after one CPP unit (n=2), and moderate headache the next day following transfusion of three CPP units (n=1). As expected in this clinically-ill patient population, D-dimer, fibrinogen, F1+2, aPTT, and TAT averaged higher than the upper limit of normal prior to transfusion and remained similar following transfusion. TGT and TEG were suppressed pre-transfusion and were improved towards normal levels following transfusion of either CPP or standard plts. There was no induction of a post-transfusion hypercoagulable state in any patient based on laboratory results. Modest increases in corrected plts count increments (x 103/mm3) were observed following CPP transfusion (one CPP unit gave CCI's of 2.3 ± 3.5; two CPP units 4.2 ± 2.8; and three CPP units 5.6 ± 2.3) compared with 21.1 ± 3.6 after one unit of standard apheresis plts. Notably, all patients had stabilization or improvement of their bleeding following a CPP transfusion including one patient with Grade 4 CNS bleeding who had resolution of neurologic symptoms with no further plt transfusions, and four patients (17%) had WHO bleeding downgraded. In conclusion, the infusion of up to three sequential units of CPP in patients with severe thrombocytopenia and active bleeding was safe without any evidence of thrombotic complications despite CPP having a procoagulant phenotype resulting from the cryopreservation process. CPP may be efficacious to stop bleeding in thrombocytopenic patients as suggested by stabilization or downgrading of WHO bleeding grades. Phase 2/3 efficacy clinical trials are now indicated. Disclosures Slichter: NHLBI / NIH: Research Funding; Genentech: Research Funding; Cerus Corporation: Research Funding; Terumo BCT: Research Funding; Cellphire: Research Funding; Department of Defense / US Army Medical Research and Material Command: Research Funding; Megakaryon: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Stock options. Dumont:US Army Medical Research and Material Command (Award W81XWH-15-C-0047) / Department of Defense: Research Funding. Cancelas:New Health Sciences, Inc.: Membership on an entity's Board of Directors or advisory committees; US Army Medical Research and Material Command (Award W81XWH-15-C-0047) / Department of Defense: Research Funding; National Institutes of Health: Research Funding; Terumo BCT: Research Funding; Cerus Corporation: Research Funding; Haemonetics, Inc.: Research Funding; Citra Labs, Inc.: Research Funding; Cellphire, Inc.: Membership on an entity's Board of Directors or advisory committees; William & Lawrence Hughes Foundation: Research Funding; Leukemia & Lymphoma Society of North America: Research Funding. Gernsheimer:Department of Defense: Research Funding; NHLBI / NIH: Research Funding. Szczepiorkowski:Fresenius Kabi: Consultancy, Membership on an entity's Board of Directors or advisory committees; Grifols: Consultancy, Research Funding; Terumo BCT: Consultancy; Cerus Corporation: Research Funding; Erydel: Research Funding; Citra Labs: Research Funding; US Army Medical Research and Material Command (Award W81XWH-15-C-0047) / Department of Defense: Research Funding; American Association of Blood Banks: Other: President-Elect. Dunbar:Verax Biomedical: Membership on an entity's Board of Directors or advisory committees; US Army Medical Research and Material Command (Award W81XWH-15-C-0047) / Department of Defense: Research Funding. Jones:US Army Medical Research and Material Command (Award W81XWH-15-C-0047) / Department of Defense: Research Funding. Rugg:US Army Medical Research and Material Command (Award W81XWH-15-C-0047) / Department of Defense: Research Funding. Prakash:US Army Medical Research and Material Command (Award W81XWH-15-C-0047) / Department of Defense: Research Funding. Hmel:US Army Medical Research and Material Command (Award W81XWH-15-C-0047) / Department of Defense: Research Funding. Ransom:US Army Medical Research and Material Command (Award W81XWH-15-C-0047) / Department of Defense: Research Funding.

INTRODUCTION/ BACKGROUND Antiphospholipid syndrome (APS) is an immunologic disorder characterized by thrombotic or obstetrical complications and persistent positivity of anticardiolipin antibodies, lupus anticoagulant, or beta-2 glycoprotein-1 antibodies. Bleeding complications in APS may sometimes occur, in the form of adrenal hemorrhage, immune thrombocytopenia (ITP), or, rarely, the lupus anticoagulant-hypoprothrombinemia syndrome (LAHS). Traditional laboratory markers of coagulation are not reliable in evaluating thrombotic or hemorrhagic risk in APS due to baseline prolongation of the prothrombin time (PT) and/or partial thromboplastin time (PTT). Thromboelastography (TEG) is a global assay of hemostasis that has been utilized in trauma surgery, emergency medicine, and chronic liver disease to identify specific coagulation defects and guide transfusion therapy. We sought to explore the role of TEG in evaluation of APS. METHODS TEG was performed on whole blood obtained from 10 patients with APS (n = 6), catastrophic APS (CAPS; n = 3), or antiphospholipid antibodies without thrombosis (n = 1). Chronic aspirin (ASA) was used as monotherapy in 2 patients; 8 were on either warfarin or enoxaparin (some in combination with ASA). Immunomodulatory treatments included hydroxychloroquine, mycophenolate, azathioprine, monthly IVIG, rituximab, or eculizumab. Prior to blood collection, patients were instructed to hold ASA for 7 days, warfarin for 5 days, or enoxaparin for 2 days, as appropriate. For patients on enoxaparin in whom cessation of anticoagulation was not feasible, heparinase was added to samples for TEG measurements. The following data was compiled for each patient: baseline PTT; lupus anticoagulant, anticardiolipin IgG and IgM, and beta-2 glycoprotein-1 IgG and IgM titers; and thrombotic, hemorrhagic, and obstetrical events. RESULTS Baseline PTT was prolonged in most patients. TEG values were within or near the normal range in almost all cases, with no consistent differences among patients with thrombotic or obstetrical APS, CAPS, or antiphospholipid antibodies without thrombosis. R time (a measure of clot initiation) was mildly prolonged in 3 cases and minimally reduced in 1. One patient with lupus, ITP, arterial and venous thrombosis, and multiple miscarriages showed minor prolongation of K time (a measure of time to maximum clot amplification) and a slight decrease in ▢ angle (a measure of thrombin burst). LY30 (a measure of fibrinolysis) was normal in all cases. One patient with LAHS and severe hemorrhagic complications had marked prolongation of R and K times and marked reduction of ▢ angle and MA (a measure of clot tensile strength), consistent with a strong bleeding phenotype. CONCLUSIONS Despite abnormal baseline coagulation studies, APS patients generally do not demonstrate a major bleeding propensity in global hemostasis assays. TEG may have potential utility in identifying APS patients with bleeding due to LAHS. Disclosures No relevant conflicts of interest to declare.

Introduction:Hemophilia causes recurrent bleeds into 'target joints' despite clotting factor replacement. Vascular remodeling associated with hemarthrosis is thought to contribute to vessel "leakiness" and perpetuated bleeding, but the underlying mechanisms remain unknown. Here, we studied the effects of joint blood volume and timing of hemostasis correction on vascular changes after induced hemarthrosis in FVIII-deficient mice, and in BALB/c mice treated temporarily with warfarin and anti-FVIII to create reversible hemostasis suppression. Methods: Mice were injured by sub-patellar puncture of the right knee to induce hemarthrosis. FVIII-deficient mice were treated with two doses of recombinant human FVIII (rhFVIII) or saline with an 8-12 hour interval. The first dose of rhFVIII was given i) 2 hours before injury (prophylaxis), ii) 2 hours after injury (early), iii) 8 hours after injury (intermediate), or iv) 16 hours after injury (late). BALB/c mice were administered 10 µg/ml warfarin in drinking water for 1 week plus 0.25 mg/kg anti-FVIII 2 hours prior to injury. This dose of warfarin yielded a ~4-fold increase in prothrombin time that was reversed with 100 IU/kg 4-Factor prothrombin complex concentrate on day 2 post-injury in one group of mice, and maintained in another. Clearance of anti-FVIII within 4 days was indicated by normalization of blood loss in tail clip experiments. On day 2 after injury, the hematocrit was determined as a measure of joint bleeding and incapacitance was monitored by left:right weight bearing. Vascularity was assessed at baseline and 1-2 weeks post-injury by high resolution musculoskeletal ultrasound with Power Doppler (MSKUS/PD) and histology with Safranin-O-Fast Green staining. Statistical analyses were conducted by Mann-Whitney test. Results: In FVIII-deficient mice, knee injury significantly reduced the mean hematocrit from 47 % to ~25 % for mice receiving late or no rhFVIII treatment (p Bleeding tendency and weight bearing deficits of the injured leg in BALB/c mice treated with warfarin and anti-FVIII were comparable to those observed in FVIII-deficient mice. Mean hematocrit decreased to 28 % (p Conclusions: FVIII prophylaxis or early treatment reduced blood loss into joints of FVIII-deficient mice and preserved joint function. However, neovascularization and vascular changes consistent with remodeling were not proportional to joint blood volume and were mostly unresponsive to short-term FVIII replacement, regardless of timing. Similarly, neovascularization in joints of hemostatically compromised BALB/c mice after induced hemarthrosis persisted despite normalization of hemostasis. Changes in vessel architecture, however, could be abrogated. This suggests that long-term hemostasis correction may protect against irreversible vascular remodeling in the joint, thought to underlie re-bleeding and development of hemophilic arthropathy. Further investigations are required to determine the effects of prolonged hemostasis correction on re-bleeding tendencies and joint health in hemophilia. Disclosures Mosnier: The Scripps Research Institute: Patents & Royalties; Hematherix LLC: Membership on an entity's Board of Directors or advisory committees; Bayer: Honoraria, Speakers Bureau; Baxalta: Honoraria, Speakers Bureau. von Drygalski:Hematherix LLC: Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Honoraria, Speakers Bureau; Novo Nordisk: Consultancy, Honoraria, Speakers Bureau; CSL-Behring: Consultancy, Honoraria, Speakers Bureau; Biogen: Consultancy, Honoraria, Speakers Bureau; Bayer: Consultancy, Honoraria, Speakers Bureau; Baxalta/Shire: Consultancy, Honoraria, Speakers Bureau.

Introduction and Objective The activated partial thromboplastin time (aPTT) and prothrombin time/ international normalized ratio (PT/INR) are the most commonly used coagulation tests (Chee et al 2008) and have become ubiquitous in medical practice despite only having been validated for very specific clinical indications (Capoor et al 2015, Pilsczek et al 2005). Indiscriminate use of these tests increases costs with little anticipated benefit for patients, and reliance on these test results to predict bleed risk may mislead care (Chee et al 2008). While staff education and development of revised practice guidelines may reduce unnecessary testing (Shojania & Grimshaw 2005), a simple process change to order panels has been shown to be associated with meaningful reductions in coagulation testing and associated costs without obvious adverse effects (Merkeley et al 2016). A prospective quality improvement initiative was conducted in the Emergency Department (ED) at St. Michael's Hospital in Toronto Canada. The ED was targeted as this was an area where coagulation test volumes were particularly high. The following strategies were implemented in order to enhance appropriate utilization of coagulation tests: PT/PTT testing options were uncoupled, ED order panels were revised, and educational materials were distributed to relevant stakeholders. These simple process changes resulted in significant reductions in unnecessary testing and meaningful cost savings. Weekly rates of PT/INR testing and aPTT per 100 ED patients decreased (17.2 vs. 38.4, rate ratio=0.45 (95% CI 0.43-0.47), p We will now broaden this initiative to other departments in our institution where high coagulation test volumes occur. We aim to enhance appropriate utilization of coagulation testing and reduce associated expenditures at an institutional level. Materials and Methods We identified three additional departments at St. Michael's Hospital where coagulation test volumes are high: Inpatient wards, outpatient clinics, and the preoperative clinic. Stakeholders in each department were identified, and department-specific change strategies were developed the in outpatient and preoperative clinics thus far. Educational sessions were held and educational materials/prompts were developed for healthcare staff in these areas. Modifications to the preoperative clinic orders sets are currently under review. Results Similar to the ED, the main outcomes are aPTT/PT test volumes and costs. Same day alternate test volumes and perioperative blood transfusions (for the preoperative clinic and inpatient wards) are balance measures. Process control charting will be used to track utilization. We plan to monitor knowledge and attitudes through focus groups and surveys. The process for changes to order sets varies by department and we believe this process change to be imperative for maximum benefit. We will be sharing our change strategy and educational materials across all hospital departments in a priority sequence. Preliminary utilization data will also be presented. Comparisons will be made both within and between departments. Conclusions Changing aPTT/PT usage is a challenge due to the plethora of stakeholders involved; however, success achieved in the ED is expected to be a predictor of success in other departments within our institution. Clinicians in the inpatient, outpatient and preoperative clinics have acknowledged the history of unnecessary testing and have demonstrated a keen willingness to address this issue. Laboratory data has facilitated the identification of areas where there appears to be substantial overuse. We anticipate that our project will result in an important decrease in aPTT/PT utilization and associated expenditures at an institutional level with no evidence of harm. Lessons learned and educational materials will be shared with the hope of reducing indiscriminate coagulation testing on a larger scale. Disclosures Sholzberg: Shire (previously Baxter, Baxalta): Honoraria, Research Funding; Novonordisk: Honoraria.

Background: Peg-asparaginasecan cause dysregulationof pro-coagulant and anti-coagulant proteins, resulting in a significant risk of venous thromboembolism(VTE) in ALL, particularly in adults undergoing induction chemotherapy. In late 2014, we adopted a policy at our institution to use prophylactic dose ofenoxaparin 40 mg daily for up to 3 weeks following the administration of peg-asparaginase. Patients are also to undergo monitoring of complete blood count, and coagulation parameters including fibrinogen and anti-thrombin. Enoxaparin may be held if patients develop severe thrombocytopenia (platelet count Methods: This is a single-center study of17 consecutive adult patients (>18 years old) treated for ALL with peg-asparaginasecontaining induction regimen before and after the establishment of institutional policy to useenoxaparinprophylaxis. Patients were identified from hospital research database. The diagnoses were verified. Medical records were reviewed for the occurrence of any clinically relevant bleeding and VTE within 3 months of receiving peg-asparaginase. Levels of coagulation parameters, whenever available, were collected at baseline and at weekly intervals for up to 4 weeks after receiving peg-asparaginase. The risk of bleeding and VTE among patients receivingenoxaparinwas compared to those who did not receiveenoxaparin. Fisher exact test was used for testing the association of categorical variable, and binomial exact test was used for computing confidence intervals. T-test or nonparametric test was used for comparing the continuous variables depending on whether or not the data were normally distributed. Results: The patient population consisted of 59% females. Mean age was 35 years. Histology consisted of Pre-B ALL in 76%, pre-T ALL in 18% and mixed lineage leukemia in 6%. 88% percent received pediatric-type chemoregimenand intramuscular peg-asparaginase; the most common doses of peg-asparaginaseincluded 2000 mg/m2 (41%) and 2500 mg/m2 (35%). Duration ofenoxaparin prophylaxis was 21 days in 66.7% and 7 days in 33.3%. Average changes in coagulation parameters at baseline and at weekly intervals following the use of peg-asparaginase therapy are highlighted in figures 1 and 2. The drop inantithrombin and fibrinogen levels was the highest during the first two weeks after the administration of peg-asparaginase. 41% of patients required cryoprecipitate (median 15 units, range 5-35 units over 4 weeks). No patients, including theenoxaparin group, had any clinically relevant bleeding event. The risk of VTE was 18% (95% confidence 4-43%); 2 out of 3 VTE events were cerebral venous thrombosis. No VTE occurred in theenoxaparin prophylaxis group (n=9), whereas 37% of patients (3 out of 8 patients), who did not receiveenoxaparin, developed VTE.Enoxaparin prophylaxis was associated with a trend towards a lower risk of VTE, however, the difference was not statistically significant (p=0.08). Conclusion: Within the limits of this study, in adult ALL patients receiving peg-asparaginase, the use of daily prophylactic dose ofenoxaparinmay not be associated with an increased risk of clinically relevant bleeding, and may have a potential to lower the risk of VTE. Patients receivingenoxaparin, however, should be carefully monitored for the need of platelet transfusion and cryoprecipitate supplementation. The difference in the risk of VTE was not statistically significant, which may be, in part, due to a small sample size.Antithrombindepletion may also contribute to a reduction in the efficacy ofenoxaparin. Larger prospective studies should be performed to validate the preliminary findings. Figure 1 Changes in prothrombin time and partial thromboplastin time Figure 1. Changes in prothrombin time and partial thromboplastin time Figure 2 Changes in antithrombin and fibrinogen levels Figure 2. Changes in antithrombin and fibrinogen levels Disclosures Armitage: Spectrum Pharmaceuticals: Consultancy; Roche: Consultancy; Conatus - IDMC: Consultancy; GlaxoSmithKline IDMC: Consultancy; ZiopharmOncology: Consultancy; Tesaro bio Inc: Membership on an entity's Board of Directors or advisory committees. Lunning:Genentech: Consultancy; AbbVie: Consultancy; Bristol-Myer-Squibb: Consultancy; Juno: Consultancy; Spectrum: Consultancy; Pharmacyclics: Consultancy; Celgene: Consultancy; Gilead: Consultancy; TG Therapeutics: Consultancy.

Introduction: Sepsis is a severe systemic inflammatory response to infection that manifests with widespread inflammation as well as endothelial and coagulation dysfunction that may lead to hypotension, organ failure, shock, and death. Disseminated intravascular coagulation (DIC) is a complication of sepsis involving systemic activation of the fibrinolytic and coagulation pathways that can lead to multi-organ dysfunction, thrombosis, and bleeding, with a two-fold increase in mortality. Elevated levels of nucleosomes released from apoptotic cells have been detected in the blood of severe sepsis patients. Procalcitonin (PCT), a propeptide of calcitonin, is a marker of inflammation of infectious origins. Both nucleosomes and PCT are associated with the inflammatory and infectious processes that play a key role in the pathogenesis of sepsis and DIC. No single biomarker or laboratory test can effectively diagnose DIC; accordingly, the International Society on Thrombosis and Hemostasis (ISTH) has developed a diagnostic algorithm based on clinical parameters that uses platelet count, prothrombin time (PT), fibrin related marker (D-dimer) and fibrinogen levels to calculate a DIC score. This study lays the groundwork for the development of a diagnostic algorithm using several markers of inflammation and infection and DIC score as parameters in assessing severity of sepsis-associated coagulopathy (SAC) in a clinical setting. Materials and Methods: De-identified serial plasma samples from patients diagnosed with sepsis-associated coagulopathy (n=137) were obtained from the University of Utah under an IRB approved protocol. The citrated plasma samples were collected from adult patients in the ICU upon admission and ICU days 4 and 8 In addition, plasma samples from healthy volunteers (n=50) were purchased from George King Biomedical (Overland, KS). Platelet count, prothrombin time, International normalized ratio (INR), D-dimer and fibrinogen levels were used to assign International Society of Thrombosis and Hemostasis (ISTH) DIC scores. Plasma samples were analyzed for procalcitonin (PCT) (Abcam, Cambridge, MA) and extracellular nucleosomes (Roche Diagnostics, Indianapolis, IN)) using a commercially available ELISA methods. In addition, markers of inflammation including interleukin 6 (IL-6), interleukin 8 (IL-8), interleukin 10 (IL-10) and tumor necrosis factor α (TNF α) were measure using the Biochip Array from Randox (Crumlin, County Antrim, UK). Results: DIC scores were calculated using the ISTH criteria and categorized into sepsis without DIC, non-overt DIC, and overt DIC. The levels of PCT were elevated in all three groups compared to normal (p0.20). Conclusions: This study demonstrates the diagnostic and prognostic value of profiling several biomarkers of inflammation and infection in patients with sepsis-associated DIC to assess the severity of illness. Elevated levels of PCT, IL-6, IL-8, IL-10 and TNF-α were observed in most patients with sepsis and DIC. Additionally, the levels of these markers show significant positive correlations to each other and to DIC score. Currently, no single biomarker can be used to confirm the diagnosis of DIC in patients with sepsis. This study provides an initial framework in developing a multiparametric profile of biomarkers in DIC for diagnostic and prognostic purposes. Disclosures No relevant conflicts of interest to declare.

Background: The direct, oral, factor Xa inhibitor, rivaroxaban, is increasingly used to provide effective anticoagulation in atrial fibrillation and venous thromboembolism. Whilst rivaroxaban does not require therapeutic monitoring there are situations when it is useful to estimate the anticoagulant effect of the drug such as during bleeding episodes or before emergency surgery. It has previously been shown that conventional coagulation tests can provide a crude estimation of anticoagulant effect of rivaroxaban if a sensitive reagent is used. In this study we explore whether rotational thromboelastometry (ROTEM) would provide a more accurate measure of rivaroxaban effect. Methods: Peak serum rivaroxaban levels were taken 3-5 hours post-dose in 121 consecutive patients established on a once-daily anticoagulation regime with rivaroxaban. Conventional coagulation tests, prothrombin time (PT) and activated partial thromboplastin time (APTT) were performed alongside rivaroxaban level and rotational thromboelastometry (ROTEM, TEM Ltd, Germany) on native citrated whole blood. PT and APTT used HemosIL Recombiplastin 2G and SynthasIL reagents (Instrumentation Laboratory (IL), USA) respectively. Rivaroxaban levels were measured using HemosIL Liquid Anti Xa kit (IL, USA) with rivaroxaban calibrators from Hyphen Biomed, France on an ACL TOP 700 coagulometer (IL, USA)). Demographic and biochemical data was collected on each patient. Results were analysed to determine if ROTEM can be used to assess the anticoagulant effect of rivaroxaban in real-world patients with different demographics and organ function. Results: Significant positive correlation was seen between rivaroxaban level and prothrombin time (PT) (R=0.796, Pearson's correlation coefficient). Weaker correlation was observed between rivaroxaban level and activated partial thromboplastin time (APTT) (R=0.425). There was modest positive correlation between the clotting time (CT) parameter using ROTEM and rivaroxaban level (R=0.328). However, when grouped into low (300ng/ml) rivaroxaban levels, the CTs show no meaningful association and therefore cannot be used as a surrogate marker to predict anticoagulant effect. There is no significant difference between the mean rivaroxaban levels for patients on 15mg rivaroxaban, those on 20mg with creatinine clearance 60ml/min (Analysis of Variance, n=121, F=2.009, P=0.159), suggesting that with dose adjustment a similar anticoagulant effect is achieved in patients with different renal function. Conclusion: Our data suggests that the correlation between rivaroxaban levels and ROTEM CT parameter is not sufficiently strong to reliably predict the anticoagulant effect of rivaroxaban and does not confer any advantage over conventional clotting tests. Disclosures Chowdary: Baxalta: Honoraria, Membership on an entity's Board of Directors or advisory committees; Biogen: Honoraria, Membership on an entity's Board of Directors or advisory committees; CSL Behring: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Sobi: Honoraria; Bayer: Honoraria; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novo Nordisk: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Drebes:Bayer: Consultancy; Bayer: Other: Educational Grant.