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Comparative effectiveness and safety of oral anticoagulants for atrial fibrillation in real-world practice: a population-based cohort study protocol
  1. Anne Holbrook1,2,3,
  2. Colin Dormuth4,
  3. Richard Morrow4,
  4. Agnes Lee5,
  5. Sue Troyan2,
  6. Guowei Li3,
  7. Eleanor Pullenyegum6
  1. 1Division of Clinical Pharmacology & Toxicology, McMaster University, Hamilton, Ontario, Canada
  2. 2Department of Clinical Pharmacology & Toxicology, St Joseph's Healthcare Hamilton, Hamilton, Ontario, Canada
  3. 3Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Ontario, Canada
  4. 4Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada
  5. 5Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
  6. 6Child Health Evaluative Sciences, Hospital for Sick Children, Toronto, Ontario, Canada
  1. Correspondence to Dr Anne Holbrook; holbrook{at}


Introduction Anticoagulants are arguably the most important drug family of all, based on the frequency and duration of their use, and the clinical importance and frequency of benefits and harms. Several direct acting oral anticoagulants (DOACs) have recently joined warfarin for the treatment of atrial fibrillation, with a resultant significant expansion in use of oral anticoagulants (OACs). Our objectives are to compare safety and effectiveness of DOACs versus warfarin in a full population where anticoagulation management is good and to identify which types of patients do better with DOACs versus warfarin and vice versa.

Methods and analysis This is a retrospective cohort study of all adults living in British Columbia who have a diagnosis of atrial fibrillation in hospital or medical service data, and a first prescription for an OAC. Coprimary outcomes are ischaemic stroke and systemic embolism (benefit) and major bleeding (harm). Secondary outcomes include net clinical benefit (composite of stroke, systemic embolism, major bleeds, myocardial infarction, pulmonary embolism and death), drug discontinuation and individual composite item occurrence. We will estimate the effects of treatment in a 2-year follow-up period, using time-to-event models with propensity score adjustment to control confounding. Secondary analyses will examine ‘as treated’ outcomes.

Ethics and dissemination The protocol, data creation plan, privacy impact statement and data sharing agreements have been approved. Dissemination is planned via conferences and publications as well as directly to drug policy leaders. Information on the overall comparative effectiveness and safety of DOACs versus warfarin in a country with high quality anticoagulation management, as well as for vulnerable subgroups, will be an important addition to the literature.


This is an Open Access article distributed in accordance with the terms of the Creative Commons Attribution (CC BY 4.0) license, which permits others to distribute, remix, adapt and build upon this work, for commercial use, provided the original work is properly cited. See:

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  • Contributors AH developed the study idea, obtained the grant funding, obtained data permissions and research ethics approvals and wrote the protocol. CD, RM and EP contributed to the study design, methodology and analysis plan and critiqued the protocol manuscript. AL and GL contributed to the methodology and critiqued the results and the protocol manuscript. ST contributed to data permissions, research ethics approvals and critiqued the protocol.

  • Funding This work was supported by a grant from the Canadian Institutes for Health Research—grant # 126150.

  • Competing interests None declared.

  • Ethics approval Hamilton Integrated Research Ethics Board Appl # 16-643-C.

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

  • Data sharing statement Data sharing agreements with PopData-BC and LifeLabs Medical Laboratory Services have been obtained prior to this study. Secure access and storage of data and data linkage are governed by Population Data BC. The necessary data access request templates, privacy impact analyses and research service agreements are complete.

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