• C Kearon, J S Ginsberg, D R Anderson, M J Kovacs, P Wells, J A Julian, B Mackinnon, C Demers, J Douketis, A G Turpie, P Van Nguyen, D Green, J Kassis, S R Kahn, S Solymoss, L Desjardins, W Geerts, M Johnston, J I Weitz, J Hirsh, M Gent, and SOFAST Investigators.
• McMaster University, Hamilton, Ontario, Canada. kearonc@mcmaster.ca
• J. Thromb. Haemost. 2004 May 1;2(5):743-9.

BackgroundThe risk of recurrence is lower after treatment of an episode of venous thromboembolism associated with a transient risk factor, such as recent surgery, than after an episode associated with a permanent, or no, risk factor. Retrospective analyses suggest that 1 month of anticoagulation is adequate for patients whose venous thromboembolic event was provoked by a transient risk factor.MethodsIn this double-blind study, patients who had completed 1 month of anticoagulant therapy for a first episode of venous thromboembolism provoked by a transient risk factor were randomly assigned to continue warfarin or to placebo for an additional 2 months. Our goal was to determine if the duration of treatment could be reduced without increasing the rate of recurrent venous thromboembolism during 11 months of follow-up.ResultsOf 84 patients assigned to placebo, five (6.0%) had recurrent venous thromboembolism, compared with three of 81 (3.7%) assigned to warfarin, resulting in an absolute risk difference of 2.3%[95% confidence interval (CI) - 5.2, 10.0]. The incidence of recurrent venous thromboembolism after discontinuation of warfarin was 6.8% per patient-year in those who received warfarin for 1 month and 3.2% per patient-year in those who received warfarin for 3 months (rate difference of 3.6% per patient-year; 95% CI - 3.8, 11.0). There were no major bleeds in either group.ConclusionDuration of anticoagulant therapy for venous thromboembolism provoked by a transient risk factor should not be reduced from 3 months to 1 month as this is likely to increase recurrent venous thromboembolism without achieving a clinically important decrease in bleeding.

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