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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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  • Twitter @carlheneghan, @JKAronson

  • Contributors CH wrote the first draft and JA contributed to this draft and both authors approved the final version.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests CH holds grant funding from the NIHR School of Primary Care Research Evidence Synthesis Working Group (project 390) and the NIHR Oxford BRC. He is editor in chief of BMJ Evidence-Based Medicine and an NIHR senior investigator. He is director of the Centre for Evidence-Based Medicine (CEBM), which jointly runs the EvidenceLive Conference with the BMJ and the Overdiagnosis Conference with some international partners, which are based on a non-profit model. CH has also received funding as

    part of a work package funded by the NIHR under its Programme Grants for Applied Research programme (RP‐PG‐0608‐10073).

    JA has written and edited articles and textbooks on adverse drug reactions, including Meyler’s Side Effects of Drugs (16th edition, 2016), its companion volumes the Side Effects of Drugs Annuals, and Stephens’ Detection and Evaluation of Adverse Drug Reactions (6th edition, 2011). He is an associate editor of BMJ Evidence-Based Medicine and a member of the CEBM (see above).

    The views expressed in this article are those of the authors and not necessarily those of the NHS, the NIHR or the Department of Health.

  • Patient consent for publication Not required.

  • Provenance and peer review Not commissioned; internally peer reviewed.