Warfarin Management for Thromboembolic Events in Atrial Fibrillation


Project Line:
Health Technology Review
Project Number:

Warfarin has been the mainstay of oral anticoagulant therapy for more than 60 years. The effectiveness of warfarin for the prevention of stroke in patients with atrial fibrillation is well established. In Canada, an estimated 200,000 to 250,000 people have this condition.

Need for Recommendations

Managing warfarin therapy is challenging because warfarin interacts with many foods and other drugs. Each patient needs an individualized warfarin dose, which takes time to determine and requires patients to go in for frequent laboratory testing of their blood to monitor their international normalized ratio (INR). The effectiveness and safety of warfarin depend on maintaining INR at therapeutic levels — too little warfarin (low INR) puts the patient at risk of stroke or other blood clots, while too much warfarin (high INR) puts the patient at risk of bleeding.

There are different approaches to managing warfarin therapy. Family doctors often follow and adjust the warfarin dose of their patients themselves, but some have the opportunity to refer patients to specialized anticoagulation clinics, where a team of health professionals will manage the warfarin therapy. In other cases, patients are able to self-test their INR and self-manage their warfarin therapy from home. Considering that location and resources can limit these options, there was a need to find out which approach is best. Specifically, the three research questions were:

Question 1: What is the role of specialized anticoagulation services or other anticoagulation management options for the optimal management of warfarin therapy?

Question 2: What is the role of patient self-testing and patient self-management for the optimal management of warfarin therapy?

Question 3: In remote areas, what types of anticoagulation management options can be recommended?

The COMPUS Expert Review Committee provided expert guidance on this project.

Key Messages

CADTH’s work on this project resulted in several key messages. 

  • Warfarin has been used for more than 60 years and is safe and effective in preventing stroke and other complications in patients with atrial fibrillation, but there’s still room for improvement in how it’s managed.
  • Managing warfarin therapy (e.g., INR testing and interpretation, dose adjustments, checking for complications) should follow a structured plan, whether it is taking place in a specialized anticoagulation clinic, a family doctor’s or specialist’s office, or other care setting.
  • A structured approach to managing warfarin therapy in any care setting should ensure ongoing patient education and follow-up, make use of dosing tools, and involve caregivers and other health professionals.
  • Patient self-testing and self-management of warfarin may be an option for select patients, but is not recommended for most.

CADTH also offers knowledge mobilization tools to support the implementation of recommendations and to assist health care professionals, policy-makers, and consumers in making well-informed decisions.

Stakeholder feedback was considered at specific stages of this project.


The Canadian Agency for Drugs and Technologies in Health (CADTH) developed the following tools to help transition our recommendations from paper into practice. To make these tools relevant to different audiences, CADTH can tailor specific tools to individual needs and settings. Contact us if you would like our assistance in tailoring any of these tools to meet your unique needs as a health care provider, policy-maker, or consumer.

Optimal Warfarin Management Newsletter


Our project on Optimal Warfarin Management for the Prevention of Thromboembolic Events in Patients with Atrial Fibrillation resulted in the following reports:

Summary Reports

Final Reports