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Patients receiving chimeric antigen receptor T cells (CAR-T cells) therapy may be particularly susceptible to coronavirus disease 2019 (COVID-19) because of several factors including the immunosuppression associated to the underlying disease and delayed cytopenias. Regrettably, data on outcomes of CAR-T recipients with COVID-19 are extremely scarce. The aim of this study was to investigate the characteristics and outcomes of COVID-19 in patients treated with CAR-T therapy. The European Hematology Association - Scientific Working Group Infection in Hematology endorsed a survey to collect and analyze data from patients developing COVID-19 after CAR-T therapy. Overall, 459 patients treated with CAR-T cells were reported from 18 European centers. The prevalence of COVID-19 cases was 4.8%. Median time from CAR-T therapy and COVID-19 diagnosis was 169 days. Severe infection occurred in 66.7% of patients and 43.3% of the subjects required admission to ICU. The COVID-19 mortality was 33%. In multivariable analysis, the disease status at the time of COVID-19 trended marginally towards adverse outcome (P=0.075). In conclusion, we documented a high fatality rate for CAR-T patients with COVID-19, supporting the need to design successful interventions to mitigate the risk of infection in this vulnerable group of patients.

Patients with previous CD19 directed chimeric antigen receptor T cell therapy (CAR T)-cell therapy have a prolonged vulnerability to viral infections. Coronavirus diseases 2019 (COVID-19) has a great impact and has previously been shown to cause high mortality in this population. Until now, real world data of the impact of vaccination and treatment on patients with COVID-19 after CD19 directed CAR T-cell therapy are lacking. Therefore, this multicenter retrospective study was conducted with data from the EPICOVIDEHA survey. Sixty-four patients were identified. The overall mortality caused by COVID-19 was 31%. Patients infected with the Omicron variant had a significantly lower risk of death due to COVID-19 compared to patients infected with previous variants (7% versus 58% (P=0.012)). Twenty-six patients were vaccinated at time of COVID-19 diagnosis. Two vaccinations showed marked but unsignificant reduction risk of COVID-19 caused mortality (33.3% versus 14.2% (P=0.379)).Also the course of disease appears milder with less frequent ICU admissions (39% versus 14% (P=0.054)) and shorter duration of hospitalization (7 versus 27.5 days (P=0.022)). Of the available treatment options, only monoclonal antibodies seemed to be effectively reducing mortality from 32% to zero (P=0.036). We conclude that survival rates of CAR T-cell recipients with COVID-19 improved over time and that the combination of prior vaccination and monoclonal antibody treatment significantly reduces their risk of death.

The advent of chimeric antigen receptor (CAR) T-cell therapy has changed the therapeutic landscape of relapsed/refractory aggressive B-cell lymphomas. Cytokine release syndrome and immune effector cell-associated neurotoxicity syndrome (ICANS) are the typical adverse events associated with this therapy. Cardiovascular toxicities have also been reported in this setting. However, there is scarce data regarding the development of sinus bradycardia after CAR T-cell therapy. Here, we detail the clinical course of 4 patients with aggressive B-cell malignancies who received CAR T-cells and developed transient and reversible sinus bradycardia in the context of ICANS. We also discuss several hypotheses behind the pathophysiology of this potential new adverse event.

Background: Patients with Philadelphia-negative chronic myeloproliferative neoplasms (MPN) typically incur high rates of infections and both drugs and comorbidities may modulate infection risk. Objectives: The present study aims to assess the effect of immunosuppressive agents on clinical outcomes of MPN patients affected by the coronavirus disease 2019 (COVID-19). Design: This is an observational study. Methods: We specifically searched and analyzed MPN patients collected by EPICOVIDEHA online registry, which includes individuals with hematological malignancies diagnosed with COVID-19 since February 2020. Results: Overall, 398 patients with MPN were observed for a median of 76 days [interquartile range (IQR): 19–197] after detection of SARS-CoV2 infection. Median age was 69 years (IQR: 58–77) and 183 individuals (46%) had myelofibrosis (MF). Overall, 121 patients (30%) of the whole cohort received immunosuppressive therapies including steroids, immunomodulatory drugs, or JAK inhibitors. Hospitalization and consecutive admission to intensive care unit was required in 216 (54%) and 53 patients (13%), respectively. Risk factors for hospital admission were identified by multivariable logistic regression and include exposure to immunosuppressive therapies [odds ratio (OR): 2.186; 95% confidence interval (CI): 1.357–3.519], age ⩾70 years, and comorbidities. The fatality rate was 22% overall and the risk of death was independently increased by age ⩾70 years [hazard ratio (HR): 2.191; 95% CI: 1.363–3.521], previous comorbidities, and exposure to immunosuppressive therapies before the infection (HR: 2.143; 95% CI: 1.363–3.521). Conclusion: COVID-19 infection led to a particularly dismal outcome in MPN patients receiving immunosuppressive agents or reporting multiple comorbidities. Therefore, specific preventive strategies need to be tailored for such individuals. Plain language summary EPICOVIDEHA registry reports inferior outcomes of COVID-19 in patients with Philadelphia-negative chronic myeloproliferative neoplasms receiving immunosuppressive therapies. Patients with Philadelphia-negative chronic myeloproliferative neoplasms (MPN) incur high rates of infections during the course of their disease. The present study was aimed at assessing which patient characteristics predicted a worse outcome of SARS-COV-2 infection in individuals with MPN. To pursue this objective, the researchers analyzed the data collected by EPICOVIDEHA, an international online registry, which includes individuals with hematological malignancies diagnosed with COVID-19 since February 2020. The database provided clinical data of 398 patients with MPN incurring COVID-19: Patients were mostly elderly (median age was 69 years); Forty-six percent of them were affected by myelofibrosis, which is the most severe MPN; Moreover, 32% were receiving immunosuppressive therapies (JAK inhibitors, such as ruxolitinib, steroids, or immunomodulatory IMID drugs, such as thalidomide) before COVID-19. Hospitalization was required in 54% of the patients, and the risk of being hospitalized for severe COVID-19 was independently predicted by Older age; Comorbidities; Exposure to immunosuppressive therapies. Overall, 22% of MPN patients deceased soon after COVID-19 and the risk of death was independently increased over twofold by Older age; Comorbidities; Exposure to immunosuppressive therapies before the infection. In conclusion, COVID-19 infection led to a particularly dismal outcome in MPN patients receiving immunosuppressive agents, including JAK inhibitors, or reporting multiple comorbidities. Therefore, specific preventive strategies need to be tailored for such individuals.

SARS-CoV-2; Hematological malignancies SARS-CoV-2; Neoplasias hematológicas SARS-CoV-2; Neoplasies hematològiques Optics COMMIT (COVID-19 Unmet Medical Needs and Associated Research Extension) COVID-19 RFP program by GILEAD Science, United States, Grant/Award Number: Project 2020-8223.

Recent studies have shown a suboptimal humoral response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) messenger RNA (mRNA) vaccines in patients diagnosed with hematologic malignancies; however, data about cellular immunogenicity are scarce. The aim of this study was to evaluate both the humoral and cellular immunogenicity 1 month after the second dose of the mRNA-1273 vaccine. Antibody titers were measured by using the Elecsys and LIAISON anti–SARS-CoV-2 S assays, and T-cell response was assessed by using interferon-γ release immunoassay technology. Overall, 76.3% (184 of 241) of patients developed humoral immunity, and the cellular response rate was 79% (184 of 233). Hypogammaglobulinemia, lymphopenia, active hematologic treatment, and anti-CD20 therapy during the previous 6 months were associated with an inferior humoral response. Conversely, age >65 years, active disease, lymphopenia, and immunosuppressive treatment of graft-versus-host disease (GVHD) were associated with an impaired cellular response. A significant dissociation between the humoral and cellular responses was observed in patients treated with anti-CD20 therapy (the humoral response was 17.5%, whereas the cellular response was 71.1%). In these patients, B-cell aplasia was confirmed while T-cell counts were preserved. In contrast, humoral response was observed in 77.3% of patients undergoing immunosuppressive treatment of GVHD, whereas only 52.4% had a cellular response. The cellular and humoral responses to the SARS-CoV-2 mRNA-1273 vaccine in patients with hematologic malignancies are highly influenced by the presence of treatments such as anti-CD20 therapy and immunosuppressive agents. This observation has implications for the further management of these patients., The authors also thank the Cellex Foundation for providing research facilities and equipment and the CERCA Programme/Generalitat de Catalunya for institutional support.

INTRODUCTION For more than two decades, the treatment of aTTPconsisted of therapeutic plasma exchange (TPE) and immunosuppressive agents. The addition of caplacizumab, a nano-antibody that binds to the A1 domain of the von Willebrand factor, inhibiting platelet aggregation, has been shown to reduce the time to resolution of thrombocytopenia, the rate of recurrence and the aTTP-related death. Real-world evidence of the effectiveness of caplacizumab is limited yet. The objective of our study was to assess the results of the introduction of caplacizumab in our internal protocol and to compare those results with the patients treated before the drug was available. METHODS A single-center retrospective observational study that evaluates the clinical characteristics and response to treatment of 18 consecutively diagnosed aTTP patients between May/14 to May/20. All patients received initial treatment with TPE and prednisone (PDN) 1 mg/Kg; the control group did not receive any other initial therapy, whereas nine patients received caplacizumab in addition to PEX and PDN once ADAMTS-13 deficiency was confirmed. Complete response (CR) was defined as the second of two consecutive days with platelets ≥150x109/L, refractoriness as the lack of platelet increase despite optimal therapy after 7 days, exacerbation as the decrease in platelet count during the first 30 days of discontinuation of TPE, and relapse as a new episode of aTTP beyond 30 days after the last TPE. All results are given as median (interquartile range). Statistical analysis was conducted using STATA/IC software. RESULTS The clinical characteristics at diagnosis of patients treated with or without caplacizumab were similar, except for a lower percentage of males and lower neurological involvement in the caplacizumab group (Table 1). Caplacizumab was started at a median of 3 days after diagnosis following ADAMTS-13 deficiency determination, and was administered during a median of 39 days (IQR 33-39). Adverse events related to caplacizumab were mild: 1 patient presented mild metrorrhagia, 1 developed pain and erythema at the puncture area and 1 suffered an urticarial dermatitis, the last case leading to the suspension of the drug since levels of ADAMTS-13 were recovered. The caplacizumab group achieved CR after a median of 4 days (IQR 3-4) vs. 6 days (IQR 5-14) in the control group (p = 0.016). Likewise, the number of TPE was lower with caplacizumab (Figure 1), with a median of 10 TPE (IQR 9-11) vs. 19 (IQR 16-23) (p = 0.001). Hospitalization time was also shorter in the caplacizumab group with a median of 12 days (IQR 12-14) vs. 26 (IQR 20-27) (p = 0.002). Finally the time of hospitalization into the intensive care unit was shorter in the caplacizumab group with a median of 3 days (IQR 2-4) vs. 4 (IQR 3-13) (p=0.1). In the caplacizumab group (median follow-up of 6.8 months), there were no refractory cases. There was 1 exacerbation before initiation of caplacizumab and 1 relapse. Both cases were treated with rituximab. In contrast, in the control group (median follow-up of 51.8 months), we observed 4 refractory cases (1 aTTP-related death), 3 exacerbations and 1 relapse; rituximab was necessary in 8 patients and a 3rd line with vincristine was administered in 4 cases. CONCLUSIONS The observed benefits of caplacizumab in our series are in line with the ones identified in randomized clinical trials. Caplacizumab can be used in combination with other therapies to attain a faster response and reduce aTTP-related complications. Disclosures Bosch: Hoffmann-La Roche: Research Funding.

Background: Mantle cell lymphoma (MCL) is still an incurable disease. While OS has significantly improved in recent years with more effective treatments, early relapse/refractoriness to induction treatment is associated with a dismal outcome (Visco, BJH 2019; Eskelund, HemaSphere 2021). Early identification of patients with MCL who will relapse early or not respond after induction could improve their management. Patients and methods: We retrospectively reviewed the characteristics of all consecutive patients diagnosed with MCL in our center from April 2000 to January 2021. The analysis included OS, PFS, DOR, age group (≤65 or >65 years old), morphology (classic vs pleomorphic/blastoid), Ki67 (24 when the relapse occurred ≤24 months or >24 months from diagnosis to the start date of the 1 st salvage treatment). Other factors currently known as relevant (SOX11, TP53 mutational status, karyotype, IGVH status, or other mutations) could not be evaluated due to the low number of patients with available data. Statistical analyses were performed with the R-4.1.0 software: Kaplan-Meier estimator for OS, PFS, DOR and median survival times, Cox regression for univariate and multivariate analyses and HR calculation, Log-rank test for comparison of OS, PFS, DOR between risk groups, and Fisher's exact test for the analysis of factors affecting POD24. Results: One hundred and twenty-five patients [Male:Female 91(72.8%):34(27.2%)] with MCL were analyzed. Age at diagnosis was ≤65 years in 60 patients (48%) and >65 years in 65 (52%), stage III-IV in 92.8%, MIPI was intermediate and high-risk in 22.6% and 53.6% respectively, Ki67 was ≥30% in 40 patients (64.5%) and MCL morphology was pleomorphic/blastoid in 40 patients (13.6%). Among 123 patients receiving at least 2 treatment lines (induction and 1 st salvage treatment), 36 (29.2%) received HiDAC and 87 (70.7%) a non-HiDAC induction. Among the 73 patients requiring salvage treatment, 45 (61.6%) were POD24. At last follow-up (FU), 50 pts were alive (40%), 7 were lost to FU (5.6%) and 68 had died (54.4%), mainly due to lymphoma-related causes (69.1%). Median OS and PFS were 7.44 and 2.52 years respectively, and median DOR was 34.9 months. There were significant differences on outcome by age group, OS was 10 vs 4.89 years (p=.0021), PFS 4.11 vs 1.64 years (p=.00012) and DOR 57 vs 15.5 months (p=.014) for patients with ≤65 and >65 years, respectively. Regarding other prognostic factors, MIPI did not impact OS, PFS nor DOR. Ki67, blastoid variant and POD24 had impact on OS in the univariate analysis, and only POD24, respectively (p=.0001) (Figure 1)) and by age group (3.32 years in POD24 for ≤65 years (p=.00057) and 3.86 in POD24 for patients >65 years (p=.0037)). Finally, we analyzed factors potentially affecting POD24, and we found significant differences with the age group and type of induction.In patients >65 years, 75.6% relapsed early (POD Conclusions: In our cohort, POD24 vs 3.86 years in POD Figure 1 Figure 1. Disclosures Abrisqueta: AstraZeneca: Consultancy, Honoraria; BMS: Consultancy, Honoraria; Roche: Consultancy, Honoraria; Abbvie: Consultancy, Honoraria; Janssen: Consultancy, Honoraria. Bobillo: F. Hoffmann-La Roche Ltd: Consultancy, Speakers Bureau; Gilead: Speakers Bureau. Carpio: Regeneron, TAKEDA, Celgene, Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other. Iacoboni: BMS/Celgene, Gilead, Novartis, Janssen, Roche: Honoraria. Gironella Mesa: BMS, Janssen: Honoraria. Palacio: Bristol Myers Squibb (BMS): Consultancy. Bosch: Roche: Membership on an entity's Board of Directors or advisory committees, Other: Travel; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Research Funding; AbbVie: Membership on an entity's Board of Directors or advisory committees, Other: Travel; Gilead: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel; TAKEDA: Membership on an entity's Board of Directors or advisory committees, Other: Travel. Marin-Niebla: Kiowa Kirin: Consultancy, Honoraria; Gilead: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Other: travel; Roche: Honoraria; Takeda: Consultancy, Honoraria, Other: travel.

INTRODUCTION: The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic raises many questions about the management of patients with significant comorbidities. Hematologic patients are usually fragile due to an important immunosuppression, so the impact of coronavirus disease (COVID-19) is yet to be determined. MATERIALS AND METHODS: We conducted a single-center retrospective observational study of patients with hematologic malignancies diagnosed with SARS-CoV-2 at Vall d´Hebron University Hospital (HUVH) between March 1st and May 31st 2020 to analyze their clinical characteristics and evolution. Patient's demographic data, underlying pathology, signs and symptoms of COVID-19, treatment received and clinical course were collected. A statistical analysis was performed to identify the possible variables associated with COVID-19 mortality. For this purpose, we used univariate and multivariable logistic regression models. RESULTS: We identified 70 patients with PCR confirmed SARS-CoV-2 infection and hematologic malignancy. The median age was 75 years (range 22-91), and 44% were female. The majority (74%) had evidence of active malignancy and 53% were receiving active therapy. Lymphoid pathology (73%) predominated over myeloid. The median number of previous lines of treatment was 0 (range 0-6), 23% had received at least 2 lines, whereas 10% underwent hematopoietic stem cell transplantation (HSCT) (5 patients allo-HSCT, 2 auto-HSCT). Half of the patients had more than one pre-existing comorbidity (17% obstructive pulmonary disease). At diagnosis the most common symptoms were fever (76%), cough (60%) and dyspnea (31%). We observed that 58% of patients presented a chest X-ray compatible with COVID-19. Regarding laboratory parameters, stood out lymphopenia (65% of patients presented COVID-19 was acquired via nosocomial infection in 23% of patients, 91% of them requiring hospitalization, 14% in the Intensive Care Unit (ICU). The median days of hospitalization since diagnosis was 17 (range 3-55). The case fatality rate (CFR) from COVID-19 was higher in hematologic patients than the one observed in non-hematologic patients at the HUVH (figure 1), being of 41% at 11 days from diagnosis. CFR was higher in patients older than 75 years old (61%), while the mortality among patients receiving active therapy was 42%. The main cause of death was acute respiratory failure (93%). In the univariate logistic regression model, age >75 years (OR 1.07; p=0.008), active malignancy (OR 5; p=0,02), >1 comorbidity (OR 5.3; p=0,049) and high levels of IL-6 (OR 8.2; p= 0.005) were statistically significant. In the multivariable logistic regression model, age ≥75 years (OR 4.4; p=0.01) and IL-6 levels at baseline > 59.6 pg/mL (OR 7.2; p=0.01) were associated with a higher mortality (table 1). The presence of an active malignancy was not a significant variable in the multivariable logistic regression model. CONCLUSIONS: Patients with hematologic malignancies and COVID-19 presented similar symptoms, signs and radiological characteristics to those described in the general population at diagnosis. In our cohort, advanced age and high IL-6 values were associated with higher mortality. Furthermore, it was observed that active hematologic disease is a factor of poor prognosis of COVID-19. Disclosures Salamero: Daichii Sankyo:Honoraria;Celgene:Consultancy, Honoraria;Novartis:Consultancy, Honoraria;Jazz Pharmaceuticals:Consultancy, Honoraria;Pfizer:Consultancy.Abrisqueta:Janssen:Consultancy, Honoraria, Speakers Bureau;AbbVie:Consultancy, Honoraria, Speakers Bureau;Roche:Consultancy, Honoraria, Speakers Bureau;Celgene:Consultancy, Honoraria.Bosch:Hoffmann-La Roche:Research Funding.

Background: Little is known about natural anti-SARS-CoV-2 antibody seroprevalence post COVID-19 and safety of vaccines in COVID-19 survivors with cancer. Methods: Among 2795 consecutive patients (pts) with COVID-19 and cancer registered to OnCovid between 01/2020 and 02/2021, we examined natural seroprevalence of anti-SARS-CoV-2 Antibodies (SC2Ab, IgM or IgG) in pts tested post-infection. We analysed prevalence and safety of SARS-Cov-2 vaccine administration in pts who underwent clinical re-assessment at participating institutions. Results: Out of 350 pts tested for SC2Ab, 318 (90.9%) had a positive SC2Ab titre post-convalescence. Neither baseline features (sex, age, comorbidities, smoking history, tumour stage/status, anticancer-therapy and primary tumour) nor COVID-19-specific features (complications, hospitalization, sequelae) were significantly associated SC2Ab status. Receipt of COVID-19 specific therapy was higher among SC2Ab+ pts (62.6% vs 40.6%, p=0.0156). Out of 593 pts with known vaccination status, 178 (30%) had received 1 dose, whilst 38 pts (6.4%) received 2 doses of mRNA based (70.2%) or viral vector vaccine (17.4%). Vaccinated pts were more likely aged ≥65 years (59% vs 48.3%, p=0.0172), with loco-regional tumour stage (56% vs 40.8%, p=0.0014), on anti-cancer therapy at COVID-19 (49.1% vs 38.2%, p=0.0168) and history of prior hospitalisation due to COVID-19 (61.8% vs 48.3%, p=0.0029). Vaccine-related adverse events were reported for 18/56 evaluable pts (32.1%) and included injection site reactions (50%), fever (44.4%), arthralgias (33.3%), fatigue (33.3%) and allergy (5.5%). No long-term vaccine-related morbidity was reported. Conclusions: We report high seroprevalence (>90%) of SC2Ab in convalescent cancer pts who survived COVID-19 irrespective of baseline demographics, oncological characteristics and COVID-19 severity. COVID-19 vaccines appear to be safe in cancer pts with history of prior infection. Clinical trial identification: NCT04393974. Legal entity responsible for the study: Imperial College London. Funding: Has not received any funding. Disclosure: D.J. Pinato: Financial Interests, Personal, Invited Speaker: ViiV Healthcare;Financial Interests, Personal, Invited Speaker: Bayer;Financial Interests, Personal, Advisory Board: Eisai;Financial Interests, Personal, Advisory Board: Amgen;Financial Interests, Personal, Advisory Board: BMS;Financial Interests, Personal, Advisory Board: Pfizer;Financial Interests, Personal, Advisory Board: Nanostring tech. A. Cortellini: Financial Interests, Personal, Advisory Board: MSD;Financial Interests, Personal, Advisory Board: BMS;Financial Interests, Personal, Advisory Board: Roche;Financial Interests, Personal, Invited Speaker: Novartis;Financial Interests, Personal, Advisory Board: SunPharma;Financial Interests, Personal, Invited Speaker: AstraZeneca;Financial Interests, Personal, Invited Speaker: Astellas. All other authors have declared no conflicts of interest.

INTRODUCTION: Deep vein thrombosis (DVT) is a frequent cause or morbidity and mortality, and multiple genetic and environmental factors are involved in its etiopathogenesis. Besides investigating about personal and familiar DVT history, thrombophilia testing is often asked by physicians in order to diagnose patients, even if current validated markers won't be decisive to set duration of treatment. DVT is a multidisciplinary management entity, so it`s important to unify the diagnosis and treatment circuit with the specialists involved, in order to get a positive impact in the prognostic of the disease. MATERIALS AND METHODS: We developed an observational and prospective study between January 2017 and December 2017 in our University Tertiary Hospital in order to register the patients with DVT that were treated in our DVT unit conformed by specialists of Hemostasis, Angiology and Intern Medicine. As secondary objectives, we wanted to know how a systematic circuit would improve the management and the complications of patients with DVT. After diagnosis in Emergency Service by Angiology -or Intern Medicine if pulmonary embolism (PE), they were sent to Hemostasis Unit within the first 7-10 days to optimize treatment according patient's necessities. After 3-6 months of starting treatment, patients were seen conjunctly by specialists of Angiology and Hemostasis to perform a doppler ultrasound and thrombophilia study in selected patients, in order to make the best decision about treatment. RESULTS: We included 172 patients with DVT, most of them were men (56.9%), the average age was 66.4 years old, and the incidence increased from 50 years old, on. Only 26.2% had a positive personal history of DVT and 18% familiar history. We found that 75 (43.6%) patients had idiopathic DVT. About anatomical localization, the majority presented in the lower limbs (83.1%) and 12.7% associated pulmonary embolism at diagnosis. All of them started treatment with LMWH, and after the first clinical visit, 26.7% continued with it, while 51.2% changed to VKA and 22.1% to DOACs. We tested only 69 patients for thrombophilia, according to guidelines (especially in incidental DVT): 23.8% were diagnosed of antiphospholipid syndrome, 19% of S protein deficiency, 14.3% of C protein deficiency and 14.3% of prothrombin mutation, as the most common findings. Patients with positive study or antiphospholipid syndrome and 21 of the 41 patients with negative study, received permanent anticoagulation. In the conjunct visit we found a 61.1% of residual/chronic DVT, 38.4% resolved, and 0.5% of recurrence (local extension). Only 18.6% of patients had post thrombotic syndrome and we didn`t see any hemorrhagic complications during the follow up period. We also identified a reduction of almost a 50% of clinical visits because of the systematic circuit. CONCLUSIONS: An ordered flow of patients diagnosed of DTV contributed in our clinical practice to avoid redundant hospital visits and complementary tests, and specially to release a better follow up of patients with a less percentage of bleeding (0%) and post thrombotic syndrome (18.6% vs 40% in world registries), as well as we found. It would be interesting to amplify the time of follow up, so that we would know if these benefits remain within time. Disclosures Bosch: Kyte: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; F. Hoffmann-La Roche Ltd/Genentech, Inc.: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Takeda: Honoraria, Research Funding; AstraZeneca: Honoraria, Research Funding; AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Celgene: Honoraria, Research Funding; Acerta: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau.

INTRODUCTION: Deep venous thrombosis (DVT) is a frequent cause or morbidity and mortality, and multiple genetic and environmental factors are involved in its etiopathogenesis. According to it, besides investigating about personal and familiar DVT history, thrombophilia testing is often asked by physicians in order to diagnose patients, even if current validated markers can't predict the risk of recurrence of the disease. METHODS: We developed an observational and prospective study between January 2017 and December 2017, in order to register the patients with DVT that were treated in our DVT unit. As secondary objectives, we wanted to know how many had an idiopathic DVT, if we tested all of them for thrombophilia, which of them stopped treatment and the results after one year of follow up. RESULTS: We included 172 patients with DVT, 56.9% were men, and the average age was 66.4 years old with an increased incidence above the 50 years old. In our study group we found 43.6% (75) of patients without major risk factors for DVT, classified as idiopathic DVT and we will refer to them in this abstract from now on. Just 36.7% of them had a positive personal history of DVT and 36.7% had familiar history. Almost all were localized in the lower limbs (98.7%) and 17.3% presented in association with pulmonary embolism (PE) at diagnosis. All of them started treatment with LMWH, and after the first clinical visit, 26.7% continued with it, while 51.2% changed to VKA and 22.1% to DOACs. Only 45 (60%) of idiopathic DTVs were tested for thrombophilia (patients younger than 60 years old, with extensive DVT, or personal or familiar history of DVT): 31 had a negative study, 11 had a positive study for hereditary thrombophilia (4 S protein deficiency, 3 C protein deficiency, 2 V Leiden factor mutation + prothrombin mutation, 1 V Leiden factor mutation, 1 prothrombin mutation), and 3 were diagnosed of antiphospholipid syndrome. All these patients with positive study or antiphospholipid syndrome received indefinite anticoagulation. From all the patients with idiopathic DVT, 77.3% received indefinite anticoagulation, 17.3% were treated for 3-6 months, 4% for >6-12 months and 1,3% for 15 months. Only one patient who stopped treatment after 3 months had a recurrent DVT and had to restart it. CONCLUSIONS: DVT is the most frequent indication for thrombophilia testing and regarding its multifactorial etiology, it must be performed specially in incidental cases. In our incidental DVT study group (with PE associated or not), we found a 31.1% of positive studies, consistent with what is expected in general DVT population, but in contrast with it is described in the literature, we found more cases of S and C deficiency than V Leiden factor and prothrombin mutations. We also had only one patient with recurrence DVT after few months of stopping anticoagulation, no thrombophilia was found. This low rate of recurrence that differs from the latest data published, might be explained by the short time of follow up that we have, so it would be interesting to increase it, as well as the number of patients in the cohort studied. There is a need for investigating new clinical and genetic scores in order to improve the poor predictive role in recurrent disease with the current thrombophilia markers. Disclosures Bosch: F. Hoffmann-La Roche Ltd/Genentech, Inc.: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Takeda: Honoraria, Research Funding; AstraZeneca: Honoraria, Research Funding; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Celgene: Honoraria, Research Funding; Acerta: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Kyte: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau.