Men had greater risk for recurrent venous thromboembolism than women.

M e t h o d s Design: Inception cohort followed for a median of 26 months (Austrian Study on Recurrent Venous Thromboembolism). Setting: 4 thrombosis centers in Vienna. Patients: 826 patients > 18 years of age (mean age 48 y, 55% women) who had a first episode of VTE and had been treated with oral anticoagulants for ≥ 3 months. Patients had received standard heparin at doses designed to keep the activated partial thromboplastin time 1.5 to 2.0 times that of the control value or had received subcutaneous low-molecular-weight heparin at therapeutic doses. Exclusion criteria were surgery, trauma, or pregnancy in the previous 3 months; known deficiency of antithrombin, protein C, or protein S; lupus anticoagulant; cancer; or need for long-term treatment with antithrombotic drugs. Women were discouraged from using oral contraceptives or hormone replacement therapy. Prognostic factors: Sex; age; presence or absence of symptomatic pulmonary embolism at the time of first VTE; duration of anticoagulation; and presence or absence of factor V Leiden, factor II G20210A, and elevated levels of factors VIII and IX. Outcomes: Recurrence of symptomatic VTE. The diagnosis of deep venous thrombosis was confirmed by venography or colorcoded duplex sonography. The diagnosis of pulmonary embolism was confirmed by ventilation-perfusion lung scanning.