Conventional-intensity was more effective than low-intensity warfarin therapy for preventing recurrent venous thromboembolism.

P a t i e n t s 738 patients (mean age 57 y, 55% men) with ≥ 1 episode of unprovoked VTE (defined as objectively confirmed, symptomatic, proximal deep venous thrombosis or pulmonary embolism that occurred in the absence of a major risk factor for thrombosis) who had completed ≥ 3 months of oral anticoagulant therapy at the conventional intensity. Exclusion criteria were other indications for warfarin therapy, contraindication to long-term warfarin therapy, known antiphospholipid antibodies, allergy to contrast medium, or life expectancy < 2 years. Follow-up was 99.9%. I n t e r v e n t i o n After stratifying for clinical center and whether the patient had completed 3 to 4 or > 4 months of initial anticoagulant therapy, patients were allocated to warfarin therapy with a target international normalized ratio (INR) of 1.5 to 1.9 (low-intensity warfarin group, n = 369) or warfarin therapy with a target INR of 2.0 to 3.0 (conventional-intensity warfarin group, n = 369).