Whether a patient's sex is associated with the risk of recurrent venous thromboembolism is unknown. We studied 826 patients for an average of 36 months after a first episode of spontaneous venous thromboembolism and the withdrawal of oral anticoagulants. We excluded pregnant patients and patients with a deficiency of antithrombin, protein C, or protein S; the lupus anticoagulant; cancer; or a requirement for potentially long-term antithrombotic treatment. The end point was objective evidence of a recurrence of symptomatic venous thromboembolism. Venous thromboembolism recurred in 74 of the 373 men, as compared with 28 of the 453 women (20 percent vs. 6 percent; relative risk of recurrence, 3.6; 95 percent confidence interval, 2.3 to 5.5; P<0.001). The risk remained unchanged after adjustment for age, the duration of anticoagulation, and the presence or absence of a first symptomatic pulmonary embolism, factor V Leiden, factor II G20210A, or an elevated level of factor VIII or IX. At five years, the likelihood of recurrence was 30.7 percent among men, as compared with 8.5 percent among women (P<0.001). The relative risk of recurrence was similar among women who had had their first thrombosis during oral-contraceptive use or hormone-replacement therapy and women in the same age group in whom the first event was idiopathic. The risk of recurrent venous thromboembolism is higher among men than women.

Research from JAMA — Identification of Patients at Low Risk for Recurrent Venous Thromboembolism by Measuring Thrombin Generation — ContextScreening of patients with venous thromboembolism (VTE) for thrombophilic risk factors is common clinical practice. Because of the large number of risk factors, assessing the risk of recurrence in an individual patient is complex. A method covering multicausal thrombophilia is therefore required.ObjectiveTo investigate the relationship between recurrence of VTE and a simple global coagulation assay measuring thrombin generation.Design, Setting, and ParticipantsProspective cohort study of 914 patients with first spontaneous VTE who were followed up for an average of 47 months after discontinuation of vitamin K antagonist therapy. The study was conducted at the Department of Internal Medicine I, Medical University of Vienna, Vienna, Austria, between July 1992 and July 2005. Thrombin generation was measured by a commercially available assay system. Patients with a previous or secondary VTE; antithrombin, protein C, or protein S deficiencies; presence of lupus anticoagulant; cancer; or pregnancy were excluded.Main Outcome MeasureObjectively documented symptomatic recurrent VTE.ResultsVenous thromboembolism recurred in 100 patients (11%). Patients without recurrent VTE had lower thrombin generation than patients with recurrence (mean [SD], 349.2 [108.0] nM vs 419.5 [110.5] nM, respectively; P<.001). Compared with patients who had thrombin generation greater than 400 nM, the relative risk (RR) of recurrence was 0.42 (95% confidence interval [CI], 0.26-0.67; P<.001) in patients with values between 400 nM and 300 nM; for patients with lower values, the RR was 0.37 (95% CI, 0.21-0.66; P = .001). After 4 years, the probability of recurrence was 6.5% (95% CI, 4.0%-8.9%) among patients with thrombin generation less than 400 nM compared with 20.0% (95% CI, 14.9%-25.1%) among patients with higher values (P<.001). Patients with thrombin generation less than 400 nM, representing two thirds of patients, had a 60% lower RR of recurrence than those with greater values (RR, 0.40; 95% CI, 0.27-0.60; P<.001).ConclusionMeasurement of thrombin generation identifies patients at low risk for recurrent VTE.

Summary: The clinical relevance of high P-selectin levels in venous thrombosis is unknown. We prospectively followed 544 patients with first unprovoked venous thromboembolism (VTE) after cessation of anticoagulation and evaluated P-selectin as a risk factor of recurrent VTE. VTE recurred in 63 (12%) patients. Patients with recurrence had significantly higher P-selectin levels than those without (45.8 mg/dl ± 16.4 vs. 40.1 mg/dl ± 13.3; p = 0.006). After four years, the probability of recurrence was 20.6% (95% confidence interval [CI] 12.6–28.5) among patients with P-selectin values above the 75th percentile of the patient population and was 10.8% (95% CI 7.2–14.3) among patients with lower values (p = 0.046). Compared to patients with low P-selectin, adjusted risk of recurrence was 1.7-fold (95% CI 1.0–2.9, p = 0.045) increased among patients with P-selectin levels exceeding the 75th percentile. We conclude that high circulating P-selectin is a risk factor of recurrent VTE.