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Anticoagulation duration after deep-vein thrombosis
inclusion). This observation is likely related to selection biases. First, at the time of study initiation, French national guidelines recommended 6 months of anticoagulation for a first unprovoked deep-vein thrombosis, making physi- cians reluctant to expose patients to an additional 18 months of treatment.23 Second, in France, relatively few patients with deep-vein thrombosis are currently referred to hospital centers, the vast majority being treated by community practitioners. Consequently, not only was recruitment much slower than expected but also mainly patients at high risk of recurrence were considered for inclusion, a factor consistent with the high prevalence of major thrombophilia in our study population (22%). Although one could argue that such patients should have been excluded from the PADIS-DVT trial, systematic screening for thrombophilia was not a prerequisite for eli-
gibility (see Online Supplement) and such a high prevalence of major thrombophilia is consistent with other studies on unprovoked VTE (e.g.; 8% and 15% of antiphospholipid antibodies, homozygous factor V Leiden or homozygous G20218A prothrombin variant in the LAFIT and ELATE trials, respectively)4,9 in which systematic detection of thrombophilia was not required.4,7,9,24 Nevertheless, extended warfarin therapy (for a target INR of 2.0 – 3.0) dramatically reduced the risk of recurrent venous throm- boembolism during the study treatment period to an extent similar to that observed in the PADIS-PE trial (Figure 3) and other trials on extended warfarin therapy.4-7
As previously reported,4-7 the risk of recurrence in the placebo group was greatest during the first months after stopping anticoagulation (cumulative risk, 38.7%, 95% CI: 19.1-58.3 at 12 months) and then increased linearly by
Figure 3. Meta-analysis of the PADIS-PE and PADIS-DVT studies. Pooled hazard ratios were calculated for the com- posite of recurrent venous thromboembolism and major bleeding and for the recurrent venous thromboembolism component. The pooled hazard ratio for the component of major bleeding is not reported as there was no major bleeding in the placebo group of the PADIS-DVT trial. HR: hazard ratio; 95% CI: 95% confidence interval; PE: pul- monary embolism; DVT: deep-vein thrombosis.
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