Deep vein thrombosis Some of Paul Kyrle and Sabine Eichinger’s recommendations about long-term prevention of recurrent venous thromboembolism

Some of Paul Kyrle and Sabine Eichinger’s recommendations about long-term prevention of recurrent venous thromboembolism (Mar 26, p 1163) do not seem to be consistent with the results of randomised trials. First, they recommend stopping anticoagulant therapy for unprovoked (spontaneous) proximal deep vein thrombosis after 3 or 6 months, even though the two trials that compared this practice with continuing warfarin treatment were stopped early because of overall superiority of long-term therapy. Second, for those who are treated with long-term warfarin, they suggest that there may be a lower risk of bleeding with low-intensity warfarin (international normalised ratio [INR] 1·5–2·0) than with conventionalintensity warfarin (INR 2·0–3·0), which would be sufficient to offset the demonstrated lower efficacy of lowintensity therapy. However, in the only study that compared low-intensity and conventional-intensity warfarin for long-term treatment of venous thromboembolism, there was no evidence of a reduction in major bleeding with low-intensity therapy (0·9 per 100 patient-years with conventional-intensity and 1·1 per 100 patient-years with low-intensity; difference 0·1 per 100 patient-years, 95% CI –0·8 to 1·1). Kyrle and Eichinger suggest that less success in keeping patients’ INR values in the target range in clinical practice than in clinical trials is likely to favour the use of low-intensity therapy because of a lower likelihood of bleeding. However, a higher proportion of INR values outside the target range,