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Diagnostic algorithms for deep vein thrombosis (DVT) include D-dimer for its high negative predictive value, thus reducing the need for imaging. Small thrombi may be associated with low D-dimer levels, increasing false negatives.To assess the sensitivity and thus the false negative rates of standard and age-adjusted D-dimer cut offs for isolated distal DVT (IDDVT) in outpatients.We enrolled consecutive outpatients with suspected DVT of the lower limbs referring to our vascular emergency department from 2009 to 2018. Patients underwent D-dimer testing (STA, Stago, cut-off: 500 μg/L), pretest clinical probability (PTP) evaluation and complete compression ultrasonography. Follow-up was 3 months.Among 3948 patients (M:1554-39%, median age 69), 486 proximal DVTs (12.3%) and 348 IDDVTs (8.8%) were diagnosed. Median D-dimer was higher in proximal than IDDVT (3960 vs 1400 μgr/L; p = 0.001). The false negative rate of the standard D-dimer cut-off was 2% (95%CI: 0.8-3.2%) for proximal DVT and 14.7% (95% CI: 11-81%) for IDDVT. The false negative rate of the age-adjusted cut-off was 4.9% (3-7%) for proximal DVT and 19.5% (95% CI: 15.4-24.7%) for IDDVT.Small calf thrombi are associated with low D-dimer levels, and age-adjusted D-dimer may be below the cut-off more frequently in subjects with IDDVT than standard cut-off D-dimer, although such D-dimer levels might exclude IDDVT that require treatment.

How to prevent recurrences after a first venous thromboembolic (VTE) event in elderly patients is still an open issue, especially because of the high bleeding risk of anticoagulation in these patients. The placebo-controlled “Jason” study aims at assessing the efficacy and safety for secondary VTE prevention in elderly patients of oral Sulodexide (Vessel®) administration, a mixture of glycosaminoglycans (Alfasigma, Bologna, Italy) which proved effective against recurrences in a general population (SURVET study) without major bleeding (MB) complications. 1450 patients, aged ≥ 75 years, after at least 3 months of anticoagulation treatment for a first VTE episode, are double-blind randomized to receive for 12 months either sulodexide 500 lipasemic units (LSUs) twice daily, or sulodexide 250 LSU twice daily + indistinguishable placebo, or indistinguishable placebo. Primary outcomes for efficacy are the composite of death for VTE and recurrent VTE, and occurrence of MB for safety. Secondary outcomes include stroke, cardiovascular death and other thromboembolic events, and MB + clinically relevant non-MB. The first patient is scheduled to be randomized in May 2020. The study protocol has been approved by AIFA (Agenzia Italiana del Farmaco) and the Ethics Committee of the coordinating center. Written informed consent will be obtained from all patients prior to study participation. Jason study is an investigator-initiated trial, promoted by “Arianna Anticoagulazione” Foundation, Bologna, Italy, and supported by Alfasigma, Bologna, Italy. Study findings will be disseminated to participant centers, at research conferences and in peer-reviewed journals. Trial registration numbers NCT 04257487; EudraCT (2019–000570-33). Electronic supplementary material The online version of this article (10.1007/s11739-020-02381-5) contains supplementary material, which is available to authorized users.

Background: The long-term risk for recurrent venous thromboembolism (VTE) during extended anticoagulation for a first unprovoked VTE is uncertain. Objectives: To determine the incidence of recurrent VTE during extended anticoagulation of up to 5years in patients with a first unprovoked VTE. Methods: MEDLINE, EMBASE, and the Cochrane CENTRAL were searched to identify randomized trials and prospective cohort studies reporting recurrent VTE among patients with a first unprovoked VTE who were to receive anticoagulation for a minimum of six additional months after completing ≥3months of initial treatment. Unpublished data on number of recurrent VTE and person-years, obtained from authors of included studies, were used to calculate study-level incidence rate, and random-effects meta-analysis was used to pool results. Results: Twenty-six studies and 15603 patients were included in the analysis. During 11631 person-years of follow-up, the incidence of recurrent VTE and fatal pulmonary embolism per 100 person-years was 1.41 (95% CI, 1.03–1.84) and 0.09 (0.04–0.16), with 5-year cumulative incidences of 7.1% (3.0%–13.2%) and 1.2% (0.4%–4.6%), respectively. The incidence of recurrent VTE was 1.08 (95% CI, 0.77–1.44) with direct oral anticoagulants and 1.55 (1.01–2.20) with vitamin K antagonists. The case-fatality rate of recurrent VTE was 4.9% (95% CI, 2.2%–8.7%). Conclusions: In patients with a first unprovoked VTE, the long-term risk of recurrent VTE during extended anticoagulation is low but not negligible. Thus, clinicians and patients should be aware of this risk and take appropriate and timely action in case of suspicion of recurrent VTE. Estimates from this study can be used to advise patients on what to expect while receiving extended anticoagulation, and estimate the net clinical benefit of extended treatment to guide long-term management of unprovoked VTE. © 2021 International Society on Thrombosis and Haemostasis.

BACKGROUND The long-term risk for major bleeding in patients receiving extended (beyond the initial 3 to 6 months) anticoagulant therapy for a first unprovoked venous thromboembolism (VTE) is uncertain. PURPOSE To determine the incidence of major bleeding during extended anticoagulation of up to 5 years among patients with a first unprovoked VTE, overall, and in clinically important subgroups. DATA SOURCES MEDLINE, Embase, and the Cochrane Central Register of Controlled Trials from inception to 23 July 2021. STUDY SELECTION Randomized controlled trials (RCTs) and prospective cohort studies reporting major bleeding among patients with a first unprovoked VTE who were to receive oral anticoagulation for a minimum of 6 additional months after completing at least 3 months of initial anticoagulant treatment. DATA EXTRACTION Two reviewers independently abstracted data and assessed study quality. Unpublished data required for analyses were obtained from authors of included studies. DATA SYNTHESIS Among the 14 RCTs and 13 cohort studies included in the analysis, 9982 patients received a vitamin K antagonist (VKA) and 7220 received a direct oral anticoagulant (DOAC). The incidence of major bleeding per 100 person-years was 1.74 events (95% CI, 1.34 to 2.20 events) with VKAs and 1.12 events (CI, 0.72 to 1.62 events) with DOACs. The 5-year cumulative incidence of major bleeding with VKAs was 6.3% (CI, 3.6% to 10.0%). Among patients receiving either a VKA or a DOAC, the incidence of major bleeding was statistically significantly higher among those who were older than 65 years or had creatinine clearance less than 50 mL/min, a history of bleeding, concomitant use of antiplatelet therapy, or a hemoglobin level less than 100 g/L. The case-fatality rate of major bleeding was 8.3% (CI, 5.1% to 12.2%) with VKAs and 9.7% (CI, 3.2% to 19.2%) with DOACs. LIMITATION Data were insufficient to estimate incidence of major bleeding beyond 1 year of extended anticoagulation with DOACs. CONCLUSION In patients with a first unprovoked VTE, the long-term risks and consequences of anticoagulant-related major bleeding are considerable. This information will help inform patient prognosis and guide decision making about treatment duration for unprovoked VTE. PRIMARY FUNDING SOURCE Canadian Institutes of Health Research. (PROSPERO: CRD42019128597).

Introduction: Co-administration of enoxaparin and a direct oral factor Xa inhibitor (xabans: apixaban, edoxaban, rivaroxaban) could give rise to the problem of overlapping the anti-Xa activity when measuring direct oral anticoagulant (DOAC) levels. We aimed to evaluate in vitro the degree of the interference of increasing enoxaparin concentrations on xaban plasma levels measured by different chromogenic anti-Xa assays with drug-specific calibrators and controls. Methods: Seven plasma samples were spiked with apixaban, edoxaban, or rivaroxaban at fixed concentration, and enoxaparin at increasing concentrations (0, 0.125, 0.250, 0.50, 1.0, 1.50, and 2.0IU/mL). The evaluated chromogenic assays were as follows: Biophen DiXaI and Biophen Heparin LRT (Hyphen BioMed), Berichrom Heparin and Innovance Heparin (Siemens), STA-Liquid Anti-Xa (Stago Diagnostics), Technochrom anti-Xa (Technoclone), and HemosIL Liquid Anti-Xa (Werfen). Results: The presence of enoxaparin caused increased DOAC levels, with over-estimation depending on the anti-Xa assay and on the heparin concentration in the sample. The smallest over-estimation was in the sample with enoxaparin 0.125IU/mL and the greatest in the sample with enoxaparin 2.0IU/mL (0%, 3.1%, and 7.4% vs 583.8%, 526.1%, and 415.2% for apixaban, edoxaban, and rivaroxaban, respectively). Biophen DiXaI showed lower interference compared to other methods (maximum over-estimation in the presence of enoxaparin 2.0IU/mL: 56.4% dosing rivaroxaban by Biophen DIXaI vs 583.8% dosing apixaban by Berichrom Heparin). Conclusion: The presence of enoxaparin interferes with xabans measurement by chromogenic anti-Xa assays causing falsely elevated DOAC levels, the over-estimation being dependent on the anti-Xa assay and on the heparin concentration in the sample.

Per porre diagnosi di sindrome da anticorpi antifosfolipidi (APS) e necessario che siano presenti almeno un criterio clinico (trombosi venosa/arteriosa o complicanza della gravidanza) e persistente positivita degli anticorpi antifosfolipidi (confermata a distanza di almeno 12 settimane). I criteri di laboratorio per definire la presenza di anticorpi antifosfolipidi sono: presenza di LAC e/o aumento degli anticorpi anticardiolipina (IgG o IgM) e/o anti s2 glicoproteina I (IgG o IgM). Le variabili che possono influenzare il risultato dei test utilizzati per la diagnostica del LAC sono numerose; la standardizzazione dei test per questa diagnostica e scarsa ed e stata riportata un’ampia variabilita inter-laboratorio in termini di sensibilita e specificita. La probabilita di errori diagnostici in senso negativo (false negativita) e positivo (false positivita) e quindi piuttosto elevata. Allo scopo di migliorare l’accuratezza diagnostica di questi test, nel 2009 lo specifico sottocomitato per la standardizzazione dei metodi dell’International Society on Thrombosis and Haemostasis (ISTH) ha aggiornato le linee guida gia pubblicate in precedenza. Il Gruppo di Studio in Coagulazione della SIPMeL ha voluto riassumere in questo articolo le linee guida raccomandate dall’ISTH. Successivamente, e stata pubblicata una diversa linea guida da parte del Clinical & Laboratory Standard Institute (CLSI) che per alcuni aspetti si pone su posizioni diverse o contrastanti. Poiche le raccomandazioni indicate dal CLSI vengono seguite da molti Laboratori, si e cercato di rivedere in modo critico queste diverse posizioni. Il Gruppo di Studio SIPMeL ritiene necessario ribadire che per porre diagnosi di APS i test per la diagnostica del LAC devono essere eseguiti seguendo le linee guida ISTH.

Summary Essentials A venous thromboembolism (VTE) diagnostic strategy is economical compared to imaging alone. Applied a VTE diagnostic strategy to a D-dimer multicenter study for cost-minimization analysis. Average diagnostic test costs for patients were significantly lower with a diagnostic strategy. Implementation of a VTE diagnostic strategy reduces the diagnostic costs for a hospital. Background The burden of healthcare costs has substantially risen in the last few decades. One possible contributing factor to this increase are the diagnostic approaches for venous thromboembolism (VTE) using only imaging to exclude a diagnosis of VTE. Objective To demonstrate cost minimization in the diagnosis of VTE by comparing standalone imaging (computed tomography pulmonary angiography and compression ultrasonography) to a published VTE diagnostic strategy incorporating assessment of pre-test probability and D-dimer testing. Methods We retrospectively reviewed data from a multicenter diagnostic accuracy study of a D-dimer reagent where consecutive outpatients (n=747) with suspected VTE, including both pulmonary embolism (n=346) and deep venous thrombosis (n=401) were evaluated. By applying a VTE diagnostic strategy and using the proportion of patients that were diagnosed as VTE-negative (n=137 for PE; n=120 for DVT), we developed a cost calculator to compare the average diagnostic test cost per suspected VTE patient, both before and after the implementation of the VTE diagnostic strategy. Results Implementation of the VTE diagnostic strategy reduced the average diagnostic test cost for a suspected PE patient by 38% and for a suspected DVT patient by 24%. Assuming the proportion of VTE suspected patients to be 30% PE and 70% DVT, the weighted average reduction in the diagnostic test cost per suspected VTE patient was 32%. Conclusion Implementation of a VTE diagnostic strategy can allow hospitals to reduce costs without compromising patient safety.

Essentials Between-lab variations of cut-off values in lupus anticoagulant detection are unknown. Cut-off values were calculated in 11 labs each testing plasma from 120 donors with 3 platforms. Major variation was observed even within the same platform. Cut-off values determined in different labs are not interchangeable. SummaryBackground Cut-off values for interpretation of lupus anticoagulant (LA) detection are poorly investigated. Aims (i) To assess whether results from healthy donors were normally distributed and (ii) the between-laboratories differences in cut-off values for screening, mixing and LA confirmation when calculated as 99th or 95th centiles, and (iii) to assess their impact on the detection rate for LA. Methods Each of 11 laboratories using one of the three widely used commercial platforms for LA detection was asked to collect plasmas from 120 healthy donors and to perform screening, mixing and LA confirmation with two methods (activated partial thromboplastin time [APTT] and dilute Russell viper venom [dRVV]). A common set of LA-positive or LA-negative freeze-dried plasmas was used to assess the LA detection rate. Results were centralized (Milano) for statistical analysis. Results and conclusions (i) Clotting times or ratios for healthy subjects were not normally distributed in the majority of cases. The take-home message is that cut-off values should be determined preferably by the non-parametric method based on centiles. (ii) There were relatively large inter-laboratory cut-off variations even within the same platform and the variability was marginally attenuated when results were expressed as ratios (test-to-normal pooled plasma). The take-home message is that cut-off values should be determined locally. (iii) There were differences between cut-off values calculated as 99th or 95th centiles that translate into a different LA detection rate (the lower the centile the greater the detection rate). The take-home message is that cut-off values determined as the 95th centile allow a better LA detection rate.

Con il termine trombofilia si identifica una condizione clinica che determina un aumento del rischio di malattia tromboembolica venosa e di alcune patologie della gravidanza. Questa condizione puo essere associata ad alterazioni ematologiche, sia congenite sia acquisite, che possono essere studiate con dosaggi quantitativi o con tecniche genetiche di biologia molecolare. L’utilita di eseguire indagini di laboratorio per identificare una condizione ereditaria di trombofilia e a tutt’oggi argomento di discussione. Da parte di diverse Societa scientifiche e Gruppi di Lavoro sono state prodotte Linee guida nelle quali si sostiene che gli unici esami validati per uno studio di screening di primo livello per la trombofilia ereditaria sono: il dosaggio di antitrombina, proteina C e proteina S e la ricerca delle mutazioni per fattore V di Leiden e protrombina G20210A. Cio nonostante, a livello di indagini di screening, viene spesso richiesto o proposto lo studio di molti altri polimorfismi con incerta utilita clinica, notevole aumento dei costi e produzione di ansie e timori ingiustificati nella popolazione esaminata. Il Gruppo di Studio di Coagulazione della SIPMeL ha voluto eseguire una ricognizione della letteratura medica per aggiornare la precedente edizione di Linee guida SIMeL sullo screening della trombofilia (2004) e in particolare per ampliare le raccomandazioni in merito alla ricerca dei polimorfismi nello studio della diagnostica della trombofilia ereditaria.

Introduction: To measure direct factor Xa inhibitor (apixaban, edoxaban, rivaroxaban) concentrations, dedicated chromogenic anti-Xa assays are recommended as suitable methods to provide rapid drug quantification. Moreover, the high-performance liquid chromatography with ultraviolet detection (HPLC-UV) is reported as a reliable quantitative technique. We investigated seven anti-Xa assays and an HPLC-UV method for measurement of apixaban and rivaroxaban levels in patients enrolled in the START-Register. Methods: A total of 127 apixaban and 124 rivaroxaban samples were tested by HPLC-UV and the following anti-Xa assays: Biophen DiXaI and Heparin LRT (Hyphen BioMed), Berichrom and Innovance Heparin (Siemens), STA-Liquid Anti-Xa (Stago Diagnostics), Technochrom anti-Xa (Technoclone), and HemosIL Liquid Anti-Xa (Werfen). Each method was performed in one of the participating laboratories: Bologna, Cremona, Florence, and Padua. Results: Our data confirmed the overestimation of apixaban and rivaroxaban levels by the antithrombin-supplemented anti-Xa method (Berichrom). Performances and reproducibility of the six anti-Xa assays not supplemented with antithrombin and the HPLC-UV method were good, with limits of quantification from 8-39ng/mL (apixaban) and 15-33ng/mL (rivaroxaban). The six chromogenic methods showed good concordances with the quantitative HPLC-UV [bias: −26.9-22.3ng/mL (apixaban), −11.3-18.7ng/mL (rivaroxaban)]. Higher bias and wider range between limits of agreement were observed at higher concentrations [200ng/mL: bias −42.2-36.8ng/mL (apixaban) and −20.1-68.9ng/mL (rivaroxaban)]. Conclusion: Overall, the anti-Xa assays not supplemented with antithrombin and the HPLC-UV method proved to be suitable for apixaban and rivaroxaban quantification.

BackgroundD-dimer levels measured during and after vitamin K antagonist withdrawal may be used in clinical practice to assess the individual risk of recurrent venous thromboembolism. Currently, direct oral anticoagulants (DOACs) are frequently used in venous thromboembolism treatment; however, their pharmacokinetics and pharmacodynamics characteristics are completely different than vitamin K antagonists. The present study aimed at comparing the results of D-dimer levels during and after anticoagulation withdrawal in patients with venous thromboembolism treated with DOACs or warfarin.Material and methodsD-dimer levels were measured in 527 patients ("cases") during DOACs treatment (T0) and after 15 (T15), 30 (T30), 60 (T60) and 90 (T90) days after their discontinuation and in 527 patients ("controls") enrolled in the DULCIS study (all treated with warfarin), matched for sex, age (+/-3 y), type of D-dimer assay and site of venous thromboembolism. Both cases and controls received anticoagulant treatment after a first venous thromboembolism event that was unprovoked or associated with weak risk factors.ResultsThe rate of positive D-dimer results was significantly higher in cases than in controls at T0 (10.8% vs 5.1%, p = 0.002) and at T30 (18.8% vs 11.8%, p = 0.019), as well as at the other time-points, though not statistically significant.ConclusionD-dimer levels during and after stopping an anticoagulant treatment for a venous thromboembolism episode differ between patients treated with a DOAC than in those treated with warfarin. Specifically designed prospective studies are warranted to reassess the use of D-dimer as predictor of the risk of recurrent venous thromboembolism in patients treated with DOACs.

In the D-dimer and ULtrasonography in Combination Italian Study (DULCIS), serial D-dimer measurement in combination with assessment of residual thrombosis (in patients with deep vein thrombosis (DVT)) identified patients who safely discontinued anticoagulation after an unprovoked venous thromboembolism (VTE).In this subgroup analysis, the value of D-dimer tests was assessed in patients with isolated pulmonary embolism (PE) compared with those with DVT, with or without PE (DVT/PE). The DULCIS database was reanalysed in relation to this target.26.8% of the DULCIS patients had isolated PE as the index event; this was more prevalent in females (34.1%) than in males (21.1%; pversus 3.8% ppy; nonsignificant) who stopped anticoagulation for negative D-dimer, but it was markedly high (11.2% ppy; pversus two (7.4%) out of 27; p=0.0085).Serial D-dimer assessment can inform on the risk of recurrent VTE and help determine the duration of anticoagulation in patients with isolated PE.

Essentials Currently, DOACs are given at fixed doses and do not require laboratory monitoring. Direct oral anticoagulant-specific measurements were performed at trough and peak. Patients who developed bleeding events showed higher DOAC plasma levels at peak. This study suggests the need of a more accurate DOAC dose assessment. Background: Direct oral anticoagulants (DOACs) are administered at fixed dose. The aim of the study was to evaluate the relationship between DOAC C-trough or C-peak plasma levels and bleeding complications in patients with non-valvular atrial fibrillation (NVAF). Methods: Five hundred sixty five consecutive naive NVAF patients were enrolled. The DOAC measurements at C-trough and at C-peak (available in 411 patients) were performed at steady state, within the first month of treatment. Major bleeding (MB), clinically relevant non-major bleeding (CRNMB), and minor bleeding (MinB), occurring during 1year of follow-up after blood sampling, were recorded. For each DOAC, interval of C-trough and C-peak levels was subdivided into four equal classes and results were attributed to these classes; the median values of results were also calculated. Results: Two hundred eight patients were on apixaban, 185 on dabigatran, and 172 on rivaroxaban. For 1-[qqqdeletezzz]year follow up for all patients, we observed: 19 MB (3.36%), 6 CRNMB (1.06%), and 47 MinB (8.31%). The prevalence of bleeding patients with anticoagulant levels in the upper classes of C-peak activity (II + III + IV) was higher than that in the lowest class. Normalized results of C-peak levels were higher in patients with bleeding than in those without bleeding. Conclusions: Bleeding complications during DOAC treatment were more frequent among atrial fibrillation (AF) patients with higher C-peak anticoagulant levels. In addition to a previous study that showed an increased risk of thrombotic complications in the patients with low C-trough levels, this study seems to indicate that patients with NVAF on DOACs would need a more accurate definition of their optimal therapeutic window.

Background High inter-individual variability of the anticoagulant plasma levels of the first three direct oral anticoagulants was previously reported. Aims of the present study were to evaluate edoxaban inter and intra-individual variability in patients with non valvular atrial fibrillation and to assess correlation between edoxaban plasma levels and coagulation screening test and renal function. Methods From January 31st 2017 to June 30th 2018, a total of 101 NVAF patients were enrolled: 48 patients were on edoxaban 60 mg and 53 on edoxaban 30 mg, once daily. Blood samples were taken at C-trough and at C-peak within the first month (15–25 days) of treatment and then at C-trough each three months. Prothrombin time (PT), activated partial thromboplastin time (aPTT), specific anti-FXa chromogenic test were performed. Creatinine clearance (CrCl) was calculated using the Cockcroft-Gault formula. Results Mean inter-individual variability expressed as overall coefficient of variation (CV%) values was lower at C-peak (CV% = 49) than at C-trough (CV% = 68). Mean CV% intra-individual variability was 26.5. No significant correlation was found between edoxaban plasma levels and CrCl (C-trough r/r2 = −0.007/0.000; C-peak r/r2 = 0.129/0.017). Correlations (r/r2), at C-trough and C-peak, between edoxaban levels and PT and aPTT, were 0.386/0.149–0.922/0.851 and 0.283/0.080–0.567/0.321, respectively. Significant discrepancies between PT or aPTT and edoxaban levels were found. Conclusions This study confirms also for edoxaban a high inter-individual variability in NVAF patients. PT and aPTT are not useful to measure this drug. As for the other two anti-FXa drugs, the absence of a significant correlation between CrCl and edoxaban plasma levels was observed.

Introduction Direct oral anticoagulant (DOAC) intra- and inter-individual variability was previously reported, but its magnitude is still considered negligible for patient management. Objective To evaluate inter- and intra-individual variability in real-world atrial fibrillation patients on dabigatran, rivaroxaban or apixaban in four Italian anticoagulation clinics and to assess the correlation between DOAC plasma concentration and creatinine-clearance (CrCl). Materials and Methods A total of 330 consecutive patients were enrolled, of which 160 were on dabigatran (70 and 90 taking 150 mg or 110 mg twice-daily, respectively), 71 on rivaroxaban (37 and 34 taking 20 mg or 15 mg once-daily) and 99 on apixaban (73 and 26 taking 5 mg or 2.5 mg twice-daily). Blood was taken at trough and peak within the first month (15–25 days) of treatment. Diluted-thrombin-time (dTT) calibrated for dabigatran and anti-FXa calibrated for rivaroxaban or apixaban was performed. Results Mean inter-individual variability expressed as overall CV values for all drugs was lower at peak (CV = 46%) than at trough (CV = 63%). Mean CV% intra-individual variability was 36.6% at trough and 34.0% at peak. Correlation with CrCl was poor for all drugs and only dabigatran at trough showed a significant correlation. Conclusion This multicenter study confirms high DOAC inter-individual variability that cannot be explained by the rate of renal clearance to which the three DOAC were subjected since the correlation with CrCl was relatively poor. This poor correlation suggests caution in using CrCl as the sole laboratory parameter to indirectly evaluate residual circulating DOAC.

Essentials Direct oral anticoagulants (DOACs) do not require laboratory monitoring currently. DOAC specific measurements were performed at trough in patients with atrial fibrillation. Patients who developed thromboembolic events showed lower DOAC plasma levels. This study supports the concept of measuring DOAC levels at steady state. Summary: Background Direct oral anticoagulants (DOACs) are administered at fixed doses without the need for dose adjustment according to laboratory testing. High interindividual variability in drug blood levels has been shown with all DOACs. To evaluate a possible relationship between DOAC C-trough anticoagulant levels and thromboembolic events, 565 consecutive naive patients with atrial fibrillation (AF) were enrolled in this study performed within the START Laboratory Registry. Methods DOAC-specific measurements (diluted thrombin time or anti-activated factor II calibrated for dabigatran; anti-activated FX calibrated for rivaroxaban or apixaban) at C-trough were performed locally at steady state within 15–25 days after the start of treatment. For each DOAC, the interval of C-trough levels, from the limit of quantification to the highest value, was subdivided into four equal classes, and results were attributed to these classes; the median values of results were also calculated. Thromboembolic complications occurring during 1 year of follow-up were recorded. Results Thromboembolic events (1.8%) occurred in 10 patients who had baseline C-trough levels in the lowest class of drug levels. The incidence of thromboembolic events among patients with DOAC C-trough levels in the lowest level class was 2.4%, and that in the remaining groups was 0%. The patients with thrombotic complications also had a higher mean CHA2DS2-VASc score than that of the total patient population: 5.3 (95% confidence interval [CI] 4.3–6.3 versus 3.0 (95% CI 2.9–3.1). Conclusion In this study cohort, thrombotic complications occurred only in DOAC-treated AF patients who had very low C-trough levels, with a relatively high CHA2DS2-VASc score. Larger studies are warranted to confirm these preliminary observations. © 2018 The Authors. Journal of Thrombosis and Haemostasis published by Wiley Periodicals, Inc. on behalf of International Society on Thrombosis and Haemostasis.

Background:Laboratory investigation with specific factor XIII (FXIII) assays plays a crucial role in diagnosis of FXIII deficiency. According to the International Society on Thrombosis and Hemostasis (ISTH), it is necessary a blank sample with iodoacetamide, provided by the kit or locally prepared, when the ammonia release assays are used, to avoid FXIII activity overestimation.Methods:In this study we set up a modification of the Berichrom FXIII chromogenic assay, in which iodoacetamide was added by the BCS analyzer in the reaction mixture of the blank sample, without modifications of the original reagents. We analyzed 100 plasma samples of outpatients with clinical symptoms suggestive of a bleeding diathesis (20 samples had FXIII activity Results:In all samples blank subtraction significantly reduced FXIII activity, mostly in the low activity range group (from 10.1% to 2.4%, pConclusions:Despite the low number of samples included in the study, the described automatic procedure seemed to decrease FXIII activity overestimation and, especially for low activity range samples (

Heparin-induced thrombocytopenia (HIT) is a prothrombotic condition and it is associated with increased in vivo thrombin generation that needs to be treated with non-heparin anticoagulants such as direct thrombin inhibitors (DTIs). DTIs require parenteral administration and are associated with a non negligible risk of major bleeding. We describe a case of HIT treated with rivaroxaban, a direct oral factor Xa inhibitor which could be used to inhibit the generation of thrombin, instead of DTIs. A 68 year-old man with a thrombosis confined to the internal gastrocnemius and soleal veins developed HIT during enoxaparin 80 mg twice a day. Enoxaparin was stopped and rivaroxaban 20 mg once a day was started. Platelet count returned to base line after 6 days from enoxaparin withdrawal. After 3 months rivaroxaban was stopped and the patient had an uneventful course. This case report supports the hypothesis that rivaroxaban may be candidate for treatment of HIT, and larger studies are justified.

Intracranial atherosclerotic disease (ICAD) is responsible for at least 10% of transient ischaemic attacks (TIA). Thrombin generation has been shown to be associated with several atherosclerotic conditions and may be relevant in the pathogenesis of TIA from ICAD. BACKGROUND: Intracranial atherosclerotic disease (ICAD) is responsible for at least 10% of transient ischaemic attacks (TIA). Thrombin generation has been shown to be associated with several atherosclerotic conditions and may be relevant in the pathogenesis of TIA from ICAD. OBJECTIVE: To evaluate the association between thrombin generation and ICAD in patients with TIA. MATERIALS AND METHODS: Consecutive patients with confirmed diagnosis of TIA by vascular neurologist were enrolled. Within 24h from diagnosis, all the patients underwent: blood samples including thrombin generation search, electrocardiography, brain CT scan, blood pressure (BP) measurement, supra-aortic echo-Doppler, transcranial Doppler (TCD) and standard echocardiogram. Thrombin generation was measured as endogenous thrombin potential (ETP) in platelet-rich plasma (PRP) and in platelet-poor plasma (PPP), in the presence and in the absence of thrombomodulin (TM). RESULTS: 120 patients (male 52.5%), aged 69±16years were enrolled. Ten patients on warfarin treatment had significantly lower ETP than the others. Among the remaining, ETP in the presence or absence of TM did not differ according to TOAST classification aetiology (large vessel vs. cardioembolic vs. lacunar vs. others). In PRP, ETP was similar in patients with ICAD and in those without (1748±160 vs. 1851±36nM·min, p=0.393), whereas, ETP measured in presence of thrombomodulin was higher in patients with than in those without ICAD (2045±99 vs. 1715±41nM·min, p=0.011). In PPP, ETP was similar in patients with ICAD and in those without, whereas thrombin peak was higher in patients with ICAD than in those without both in the presence (165±17 vs. 130±5nM, p=0.036) and in the absence of TM (178±19 vs. 142±5nM, p=0.037). CONCLUSION: ETP measured in presence of TM is enhanced in patients with ICAD, supporting that thrombomodulin-protein C pathways is relevant in TIA from ICAD. These hypothesis-generating data suggest that thrombin generation may be relevant in cerebral ischaemia from intracranial disease, and justify larger studies.

no abstract available

Essentials Predicting recurrences may guide therapy after unprovoked venous thromboembolism (VTE). We evaluated the DASH score in 827 patients with unprovoked VTE to verify prediction accuracy. A DASH score ≤ 1 had a cumulative recurrence risk at 1 year of 3.6%, as predicted by the model. The DASH score performed better in younger (< 65 years old) subjects. Summary: Background The DASH prediction model has been proposed as a guide to identify patients at low risk of recurrence of venous thromboembolism (VTE), but has never been validated in an independent cohort. Aims To validate the calibration and discrimination of the DASH prediction model, and to evaluate the DASH score in a predefined patient subgroup aged > 65 years. Methods Patients with a proximal unprovoked deep vein thrombosis (DVT) or pulmonary embolism (PE) who received a full course of vitamin K antagonist or direct oral anticoagulant (> 3 months) and had D-dimer measured after treatment withdrawal were eligible. The DASH score was computed on the basis of the D-dimer level after therapy withdrawal and personal characteristics at the time of the event. Recurrent VTE events were symptomatic proximal or distal DVT/PE, and were analyzed with a time-dependent analysis. Observed 12-month and 24-month recurrence rates were compared with recurrence rates predicted by the DASH model. Results We analyzed a total of 827 patients, of whom 100 (12.1%) had an objectively documented recurrence. As compared with the original DASH cohort, there was a greater proportion of subjects with a ‘low-risk’ (≤ 1) DASH score (66.3% versus 51.6%, P < 0.001). The slope of the observed versus expected cumulative incidence at 2 years was 0.71 (95% confidence interval 0.51–1.45). The c-statistic was lower for subjects aged > 65 years (0.54) than for younger subjects (0.72). Conclusions These results confirm the validity of DASH prediction model, particularly in young subjects. The recurrence risk in elderly patients (> 65 years) was, however, > 5% even in those with the lowest DASH scores.

Genetic and nutritional factors are determinants of total plasma homocysteine (tHCy) whose increased levels play a pathogenic role in atherothrombosis and cardiovascular disease. This study investigated the influence of sex, age, creatinine, serum folate, vitamin B12 and vitamin B6 (pyridoxal- 5-phosphate, PLP) on fasting (FtHCy) and two hour postmethionine loading levels of tHCy in 147 apparently healthy subjects (M/F= 82/65, age range: 14-94 y). FtHCy was higher in men than women (9.89 vs 8.00 μmol/L, p0.01). In males, the main determinants of FtHCy were age and folate levels, respectively explaining 20.5% and 19.0% of FtHCy variance. In women, besides age (22.6%), vitamin B12 (17.8%) rather than folate was a major determinant of FtHCy. Two hour postload tHCy, expressed both as absolute value (PML) and as the difference between 2 hour postload tHCy and FtHCy (delta tHCy) was negatively correlated with folate in both sexes, and with vitamin B12 and age in women only. In males folate was the main determinant, explaining 20% of the variance of postload values, while in females vitamin B12 and PLP were predominant, explaining respectively 40% and 20% of that variance. Age was not among the main determinants of postload values in either sex. These results demonstrate that age and vitamin status differently influence both the fasting and the postmethionine plasma homocysteine levels in normal subjects.

Objectives Few data are available on thrombophilic risk factors and clinical outcome in patients undergoing percutaneous transluminal angioplasty (PTA) for peripheral arterial disease (PAD). We investigated the role of homocysteine, fibrinogen, Factor VIII (FVIII), lupus anticoagulant (LAC) and FII G20210A, and FV R506Q (FV Leiden) mutations as prognostic factors in 230 patients who underwent PTA for PAD (Fontaine’s stages: IIb through IV; aged 69 ± 1 years). Design and methods A prospective study. Major adverse cardiovascular events (MACE) were the composite ‘end’ point. Results During the follow-up (24.3 ± 1.5 months), 96 (41.7%) patients reached the ‘end’ point. According to Cox regression analysis, diabetes and critical limb ischaemia were predictors of MACE, whereas each single thrombophilic alteration was not. Thrombophilic alterations were more frequent in patients that reached the ‘end’ point, and the patients with two alterations (hazard ratio (HR) 2.55 confidence interval (CI): 1.20–5.46, p = 0.015) and those with three or more alterations (HR 2.91 CI: 1.31–6.45, p = 0.009) had an increased risk for MACE versus those without alterations. Thrombophilic alterations were not associated with limb loss during the follow-up. Conclusion The presence of multiple thrombophilic alterations in patients who underwent PTA for PAD is associated with increased risk of arterial thrombotic events.

SummaryD-dimer and residual venous obstruction (RVO) have been separately shown to be risk factors for recurrent venous thromboembolism (VTE) after a first episode of unprovoked proximal deep-vein thrombosis (DVT). It was the objective of this study to assess the predictive value of D-dimer and residual vein obstruction (RVO), alone and in combination, for recurrence after provoked DVT of the lower limbs. A total of 296 consecutive patients with a first episode of symptomatic provoked proximal DVT were evaluated at a university hospital in Bologna, Italy. On the day of anticoagulation withdrawal (T0), RVO was determined by compression ultrasonography. D-dimer levels (cut-off: 500 ng/ml) were measured at T0 and after 30 ±10 days (T1). The main outcome was recurrent VTE during a two-year follow-up. D-dimer was abnormal in 11.6% (32/276) and 31% (85/276) of subjects at T0 and at T1, respectively. RVO was present in 44.8% (132/294) of patients. Recurrence rate was 5.1% (15/296; 95% confidence interval [CI]: 3–8%; 3% patient-years; 95% CI: 2–5 %). An abnormal D-dimer either at T0 or at T1 was associated with an adjusted hazard ratio (HR) for recurrence of 4.2 (95% CI:1.2–14.2; p=0.02) and 3.8 (95%CI: 1.2–12.1; p=0.02), respectively, when compared with normal D-dimer. The HR for recurrence associated with RVO was not significant, and RVO did not increase the recurrence risk associated with an abnormal D-dimer either at T0 or T1. In conclusion, an abnormal D-dimer during vitamin K antagonist (VKA) treatment or at one month after VKA withdrawal is a risk factor for recurrence in patients with provoked DVT, while RVO at the time of anticoagulation withdrawal is not.

Background: Venous thromboembolism (VTE) is a major complication of myeloma therapy recently observed with the increasing use of up-front thalidomide and dexamethasone (thal–dex). The pathogenesis of thal-induced VTE is not well recognized, and the role of prothrombotic factors, especially of thrombophilic abnormalities, is not yet determined. Material and methods: Two hundred and sixty-six patients with newly diagnosed multiple myeloma (MM) were primarily treated with thal–dex in preparation for subsequent high-dose therapy and autologous stem-cell transplantation. Out of these 266 patients, 190 were evaluated for thrombophilic alterations at baseline, and 125 of them were also re-assessed after thal–dex therapy. Results: The presence of genetic thrombophilic polymorphisms among patients with MM was superimposable to that of normal controls and was associated with a twofold increase in the relative risk of VTE. aAPCR and elevated factor VIII levels were frequent, albeit transient, alterations and were not associated with a significant increase in the risk of VTE. Two hundred and forty-six patients received a thromboprophylaxis with fixed low-dose warfarin (1.25 mg/day) during thal–dex therapy. Of these patients (or 10.6%), 26 had symptomatic VTE events. Their patients-years rate of VTE (35.5%) was significantly lower in comparison with the 86.2% rate recorded among the first 19 patients who initially entered the study and did not receive any kind of thromboprophylaxis (P = 0.043). Conclusions: On the basis of these data, a baseline thrombophilic work up is not recommended in patients with receiving up-front thal–dex. For these patients, fixed low-dose warfarin may be a valuable prophylaxis against VTE.

The PROLONG randomized trial showed that a normal D-dimer (D-d) 1 month after anticoagulation suspension for unprovoked venous thromboembolism (VTE) was associated with a low risk of late recurrences (4.4% patient years). However, it is unknown whether D-d changes subsequently. The aim of this prospective multicenter study was to assess D-d time course and its relation with late recurrences in patients with normal D-d 1 month after anticoagulation suspension for a first episode of unprovoked VTE. D-d was measured with a qualitative method (Clearview Simplify D-dimer; Inverness Medical Professional Diagnostics). Patients with a normal D-d 1 month after stopping anticoagulation repeated D-d testing every 2 months for 1 year. D-d was normal in 68% (243/355) of patients 1 month after anticoagulation suspension. Patients in whom D-d became abnormal at the third month and remained abnormal afterward had a higher risk of recurrence (7/31; 27% patient years; 95% confidence interval [CI]: 12-48) than patients in whom D-d remained normal at the third month and afterward (4/149; 2.9% patient years; 95% CI: 1-7; adjusted hazard ratio: 7.9; 95% CI: 2.1-30; P = .002). Repeated D-d testing after anticoagulation suspension for a first episode of unprovoked VTE could help tailor the duration of treatment. This trial is registered at http://clinicaltrials.gov as NCT00266045.

SummaryHeparin-induced thrombocytopenia (HIT) is a life-threatening complication of heparin treatment; the prognosis depends on early and accurate diagnosis, and prompt start of alternative anticoagulants. Because of high sensitivity, the commercially available immunologic assays are widely used, though not suited to be run on single samples and with a turnaround time of 2–3 hours. We evaluated two new, rapid, automated, semi-quantitative chemiluminescent immunoassays in HIT suspected patients: HemosIL® AcuStar HIT-IgG(PF4-H) (specific for IgG anti- PF4/heparin antibodies) and HemosIL® AcuStar HIT-Ab(PF4-H) (detecting IgG, IgM and IgA anti-PF4/heparin antibodies) (both from Instrumentation Laboratory). A total of 102 patients with suspected HIT were included; HIT was diagnosed in 17 (16.7%). No false negative cases were observed using either the HemosIL AcuStar HIT-IgG(PF4-H) or the HITAb(PF4-H) assay (sensitivity and negative predictive values = 100%; negative likelihood ratios

SummaryThe natural history of calf deep-vein thrombosis (DVT) is still uncertain and it is debated whether it warrants to be diagnosed and treated. We aimed to investigate the complication rate of untreated isolated calf DVT (ICDVT). Symptomatic outpatients were prospectively managed with serial compression ultrasonography (SCUS). Those without proximal DVT and with likely pre-test clinical probability (PCP) or altered D-dimer received immediate subsequent complete examination of calf deep veins (CCUS) by a different operator. The result of CCUS was kept blind both to the managing doctor and the patient and disclosed after three months. Primary outcome was the rate of venous thromboembolism at three months. We examined 431 subjects (196 males; median age 68.0 years) in whom five outcomes were recorded (1.2%; 95% confidence intervals [CI]: 0.4–2.7). If CCUS results had been available, outcomes would have been recorded in 3/424 patients (0.7%; 95% CI: 0.2–2.1) with two events in subjects negative at both serial and complete CUS. ICDVT was diagnosed in 65 subjects (15.3%; 95% CI: 12–19); of whom 59 remained uneventful (one was lost to follow-up). A significant higher rate of outcomes was recorded in subjects with than without ICDVT (5/64; 7.8%; 95% CI: 3–17 vs. 3/351; 0.8%; 95% CI: 0–2; p=0.003). However, after excluding two events picked at serial CUS in subjects with ICDVT, the difference became barely significant (3/64; 4.7%; 95% CI: 1–13; p=0.049). Thrombotic evolution of untreated ICDVT in high-risk subjects may be relevant. Larger studies are needed to address this issue.

SummaryFew data are available on thrombophilic risk factors and progression of atherosclerotic peripheral arterial disease (PAD). Thrombophilic alterations can be an aggravating factor when arterial stenoses are present. In a cross-sectional study, we evaluated the presence of the thrombophilic factors fibrinogen, homocysteine, factor (F)VIII, lupus anticoagulant (LAC), FII G20210A, and FV R506Q mutations in 181 patients with PAD at Fontaine’s stage II (claudication), in 110 patients with critical limb ischaemia (CLI), and in 210 controls. Fibrinogen was higher in patients with CLI vs. those with claudication and controls (427.9 ± 10.5 vs. 373.1 ± 5.2 vs. 348.9 ± 7.0 p=0.001, respectively). Homocysteine and FVIII were higher in patients with PAD than in controls, but were similar in patients with CLI and claudication. The prevalence of LAC increased in patients with CLI vs. those with claudication and controls (21.4% vs. 7.8% vs. 5.2% p

Background The optimal dose of low-molecular-weight-heparin (LMWH) to prevent venous thromboembolism (VTE) after bariatric surgery remains controversial. Aim The aim of this study was to evaluate the pharmacodynamic parameters of two doses of the LMWH parnaparin administered to patients undergoing bariatric surgery. Methods Patients were enrolled in a multicentre, open label, pilot study and were randomised to receive 4250 IU/day [n = 36; 30 females; median age: 38 years (23-56); median BMI: 46.7 Kg/m2 (36.5-58.8)] or 6400 IU/day [n = 30; 24 females; median age: 42 years (22-63); median BMI: 43.7 Kg/m2 (36.1-64.1)] of parnaparin s.c. for 7-11 days. The pharmacodynamic effects of parnaparin were analysed by measuring the anti Factor Xa activity on day 0 (12 hours after the first parnaparin injection), day 4 and day 6 after surgery (before and 4 hours after parnaparin administration). Results In 98.3% of patients receiving 4250 IU/day the peak anti-Xa levels were in the range of 0.1-0.4 IU/ml. Higher anti-Xa levels were observed in patients receiving 6400 IU/day: in 62.3% of these patients the peak anti-Xa levels were greater than 0.4 IU/ml. The anti-Xa levels measured 4 hours after injection on days 4 and 6 were not statistically correlated with BMI for either dose of-parnaparin (p = 0.077 and p = 0.401 for 4250 or 6400 IU/day, respectively). Conclusion The dose of 4250 IU/day seems adequate to achieve prophylactic anti-Xa levels in morbid obese patients undergoing bariatric surgery. Conversely, most of the patients receiving 6.400 IU/day show anti-Xa levels higher than the recommended prophylactic values.

SummaryD-dimer testing is widely applied for exclusion of deep-vein thrombosis (DVT) and pulmonary embolism (PE).We report on a multicenter performance evaluation of a new particle-enhanced immuno assay Innovance™ D-Dimer. Innovance D-Dimer assay was performed in 1,543 frozen samples from outpatients suspected of DVT and/or PE enrolled in three management studies as well as in a routine clinical practice. Samples were assayed on BCS®/BCS® XP, BCT® as well as Sysmex® CA-7000, CA-1500 and CA-560 analyzers (cut-off on all analyzers: 0.5 mg/l). Stratus® CS D-Dimer and Vidas® D-Dimer Exclusion were used for comparison. The precision study indicated total coefficients of variation ranging from 2.1% to 8.4% depending on the analyzer and on the sample. Sensitivity and negative predictive values were above 99% and their lower 95% confidence interval were equal or above 97.4% and 98.6%, respectively. Specificity ranged from 38.2% to 40.4% and the respective lower 95% confidence intervals from 35.5% to 37.7%. Area under the curve was 0.90 for all assay systems except for Innovance D-Dimer with BCT (0.89).Two samples from patients with distal DVT tested negative with all assay systems. One patient with high pre-test clinical probability and proximal DVT tested negative with Vidas D-Dimer Exclusion. Our data indicate that the performances of Innovance D-Dimer, regardless of the analyzer, are similar to the reference methods, and that this assay can be used for the exclusion of venous thromboembolic disease.

Background and objectives: To assess the predictive value of D-dimer (D-d) and Factor VIII (FVIII) in combination for recurrent venous thromboembolism (VTE) after vitamin K antagonist (VKA) therapy suspension. Design and methods: Consecutive outpatients with a first episode of idiopathic proximal deep vein thrombosis of the lower limbs were enrolled on the day of VKA suspension. After 30+/−10 days, D-d (cut-off value: 500 ng/mL), chromogenic FVIII activity and inherited thrombophilia were determined. Follow-up was 2 years. Results: Overall recurrence rate was 16.4% (55/336; 95% CI:13–21%). The multivariate hazard ratio (HR) for recurrence was 2.45 (95% CI: 1.24–4.99) for abnormal D-d and 2.76 (95% CI:1.57–4.85) for FVIII above the 75th percentile (2.42 U/mL) after adjustment for age, sex, thrombophilia, VKA duration and residual venous obstruction. When compared with normal D-d and FVIII, the multivariate HR was 4.5 (95% CI: 1.7–12.2) for normal D-d with FVIII above 2.42 U/mL and 2.7 (95% CI: 1.2–6.6) and 7.1 (95% CI:2.8–17.6) for abnormal D-d with FVIII, respectively, below and above 2.42 U/mL. Interpretation and conclusions: D-d and FVIII at 30+/−10 days after VKA withdrawal are independent risk factors for recurrent VTE.

Essentials Prothrombin and partial thromboplastin time (PT/PTT) measure direct oral anticoagulants (DOACs). PT, PTT and specific tests for DOACs were performed on patients treated for atrial fibrillation. Normal PT/PTT don't exclude DOAC activity and their prolongation doesn't confirm DOAC action. The use of PT or PTT to evaluate DOAC activity could cause dangerous misinterpretations. Summary: Background Prothrombin time (PT) and activated partial thromboplastin time (APTT) have been proposed to measure the effect of oral anti-activated factor X (FXa) or anti-activated FII drugs, respectively. Aims To evaluate the relationships and responsiveness of PT and APTT versus direct oral anticoagulant (DOAC) concentrations measured with specific coagulation tests performed with different platforms in four Italian anticoagulation clinics. Methods Six hundred and thirty-five patients with atrial fibrillation participated in the study: 240 were receiving dabigatran, 264 were receiving rivaroxaban, and 131 were receiving apixaban. Blood was taken at trough and peak within the first month (15–25 days) of treatment. PT, APTT, diluted thrombin time (dTT) calibrated for dabigatran and anti-FXa calibrated for rivaroxaban or apixaban were determined. Results For dabigatran, the correlation between APTT and dTT ranged from r = 0.80 to r = 0.62. For rivaroxaban, the correlation between the anti-FXa assay and PT ranged from r = 0.91 to r = 0.73. For apixaban, the correlation between the anti-FXa assay and PT was lower than for the two other drugs (r = 0.81 to r = 0.54). Despite the above significant correlations, the responsiveness of PT or APTT was relatively poor. A discrepancy between global testing and DOAC plasma concentrations was shown in a considerable proportion of patients, depending on the platform and drug, with values ranging from 6% to 62%. Conclusions Overall, poor responsiveness of the screening tests to DOAC concentrations was observed. PT and APTT normal values cannot exclude DOAC anticoagulant activity, and PT or APTT prolongation is not always associated with DOAC anticoagulant effect as determined with specific tests.

Background The risk of heparin induced thrombocytopenia (HIT) associated with low molecular weight heparin (LMWH) for treatment of superficial vein thrombosis (SVT) is uncertain. As a result the necessity of platelet count monitoring is unclear in this setting. Aims To assess the risk of HIT in outpatients treated with LMWH for SVT. Methods In a prospective single centre study we included all symptomatic outpatients in whom a real-time B-mode and color Doppler ultrasonography examination revealed SVT without DVT. Patients treated with vitamin K antagonists or fondaparinux were excluded. Patients received full dose enoxaparin for 1 week followed by half therapeutic dose for 3 weeks or parnaparin 8500 UI aXa for 10 days followed by 6400 UI aXa once daily for 20 days. Platelet count was performed on the day of diagnosis (D0) and 7 (D7), and 14 (D14) days afterward. Primary outcomes were the rate of thromboembolic events and of HIT during a 3-month follow-up. Results 678 outpatients (age: 64.7 ± 16.2 years, male: 42.0%) were evaluated. During follow-up, 7 venous thrombo-embolic events were recorded (1.03% CI 95%: 0.50–2.11%), while no major bleeding was observed (0.0% CI 95%: 0.0–0.56%). Platelet count was 255 ± 93 × 109/L at D0, 245 ± 93 × 109/L at D7 (p = 0.204 vs. D0) and 261 ± 116 × 109/L at D14 (p = 0.405 vs. D0). No fall in platelet count > 50% and no case of HIT were recorded (HR 0.0% CI 95%: 0–0.56%). Conclusions A 4-week LMWH treatment for SVT is associated with an incidence of HIT lower than 0.6% and platelet count monitoring may be omitted in this setting.

Summary. Background: The A > G polymorphism at position 19911 of the prothrombin gene is associated with increased plasma prothrombin levels but its role as a risk factor for venous thromboembolism (VTE) is not established. Objective: To investigate the role of prothrombin 19911 A > G polymorphism in the risk of VTE in patients with heterozygous prothrombin 20210GA or factor (F) V Leiden and in those without thrombophilia. Patients and methods: Case–control study of 793 patients with prothrombin 20210 GA (n = 167) or FV Leiden (n = 198), and without thrombophilia (n = 428), and of 795 healthy individuals with the corresponding coagulation profile, investigated for the presence of prothrombin 19911 A > G. Plasma prothrombin levels were measured in 342 individuals. Results: Prothrombin 19911 A > G did not increase the risk of VTE in carriers of prothrombin 20210 GA [odds ratio (OR) 1.2, 95% CI (95% CI) 0.8–1.8] but significantly increased the risk in carriers of FV Leiden (OR 2.1, 95% CI 1.3–3.4) and in patients without thrombophilia (OR 1.5, 95% CI 1.0–2.2). Higher plasma prothrombin levels in carriers of prothrombin 19911 A > G polymorphism than in non-carriers were found among individuals without thrombophilia (P =0.05) and with FV Leiden (P = 0.07), but not in carriers of prothrombin 20210 GA (P = 0.2). Conclusions: Prothrombin 19911 A > G polymorphism was independently associated with a 1.5-fold increased risk of VTE and increased 2-fold the risk of VTE associated with FV Leiden, both increases statistically significant. No effect was observed in carriers of prothrombin 20210 GA, perhaps because this polymorphism has a stronger influence on plasma prothrombin levels than the prothrombin 19911 polymorphism.