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Primary care
Shared decision making for thromboembolic prophylaxis in non-valvular atrial fibrillation: promise and problems with the American College of Cardiology’s AnticoagEvaluator (based on SPARCtool)


Background and methods People with atrial fibrillation face an increased risk of thromboembolic events, and deciding on an antithromboembolic strategy in non-valvular atrial fibrillation is a prime opportunity for shared decision making. Therefore, tools facilitating this process are highly desirable. The American College of Cardiology strives for such with its ‘AnticoagEvaluator’, which is based on Peter Loewen’s ‘SPARCtool’. However, it appears these tools were released without standard peer review. Therefore, an analysis of these tools was undertaken to evaluate their soundness, namely proper use of baseline risk and effect estimates from the available evidence.

Results Despite Loewen’s laudable idea and the American College of Cardiology developing AnticoagEvaluator based on Loewen’s work, both tools have a flaw: they use relative effect estimates based on composite outcomes (thromboembolic and haemorrhagic) that do not match the baseline risk to which they are applied (thromboembolic). This can lead to importantly inaccurate impressions of therapeutic efficacy. This analysis explores this issue and offers potential solutions.

Conclusions The American College of Cardiology releasing and promoting a tool that gives misleading impressions of therapeutic efficacy is of considerable importance, though SPARCtool should also be corrected as a matter of importance. Means to correct the tools are identified herein, and if corrected, these tools stand to better fulfil their intended purpose as important and useful additions for clinical and shared decision making. This article’s analysis of the tools has a directly practical purpose, but it also serves as an instructive example of key elements of evidence-based medicine and shared decision making.

  • biostatistics
  • clinical epidemiology
  • atrial fibrillation
  • non-valvular atrial fibrillation
  • evidence-based medicine
  • shared decision-making
  • decision aid
  • direct oral anticoagulants
  • novel oral anticoagulants
  • warfarin
  • vitamin K antagonists
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