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General medicine
Extending anticoagulation treatment for unprovoked venous thromboembolism
  1. Carl Heneghan,
  2. Jeffrey Aronson
  1. Centre for Evidence-Based Medicine, University of Oxford, Oxford, UK
  1. Correspondence to Professor Carl Heneghan, Centre for Evidence-Based Medicine, University of Oxford, Oxford OX2 6GG, UK; carl.heneghan{at}

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Two recent systematic reviews have addressed uncertainties about extending anticoagulation beyond the usually recommended periods in patients with unprovoked venous thromboembolism.

The appropriate duration of anticoagulation after a first episode of unprovoked venous thromboembolism (VTE) is undecided. For instance, the UK’s National Institute for Health and Care Excellence recommends extending anticoagulation beyond 3 months in patients with an unprovoked VTE if the risk of recurrence is high and the risk of major bleeding low.1 The risk of recurrence after an unprovoked episode is greater than if the episode is provoked.

VTE is considered to have been unprovoked when there is no preceding major clinical risk factor, such as surgery or trauma, no active cancer or thrombophilia, no family history of VTE and no hormonal therapy (an oral contraceptive or hormone replacement therapy). The decision to extend treatment is influenced by the risk of recurrence, the risk of bleeding and the preferences of the patient and physician. Evidence that informs recurrence rates helps decision-making.

Systematic reviews

The rate of recurrent VTE has been studied in a recent BMJ systematic review, in patients with a first episode of unprovoked VTE who had taken an anticoagulant for at least 3 months and then stopped. The review included 18 studies (14 randomised controlled trials and 4 prospective cohort studies; 7515 patients); all were of high quality, …

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