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The 3-6 million Americans with atrial fibrillation face a five-fold risk of stroke.* Lifelong oral anticoagulation, with either warfarin or a new oral anticoagulant (NOAC), is recommended for most patients to prevent stroke.

Patients and their physicians have a choice among different drugs but with little evidence to guide the choice.

Leveraging the rich data from OptumLabs®, Mayo Clinic researchers investigated whether clinical trial results of the new drugs apply to patients in everyday practice, and addressed new questions that cannot be answered by the trials.  

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Comparative effectiveness and safety

NOACs are generally effective and safe across various patient populations. When comparing one NOAC to another, they have similar effectiveness but different safety profiles.


Fewer than half of patients adhered to the drugs. Adherence appears to be most important in patients with high baseline risk, whereas the benefit of anticoagulation may not outweigh the harm in low-risk patients.

Inappropriate dosing

One in six patients was prescribed with a NOAC dose inconsistent with the FDA labeling. Overdosing was associated with worse safety without a benefit in effectiveness. Underdosing was associated with worse effectiveness without a benefit in safety.

See publications

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Guiding clinical decisions

This research has yielded over 10 high-impact publications and interest from many health care stakeholders. The Mayo team is now leveraging findings to build patient shared decision aids and other clinical decision support tools that doctors can use for anticoagulants.




*Centers for Disease Control and Prevention. Atrial fibrillation fact sheet. Published Aug. 22, 2017. Accessed Sept. 27, 2017.  


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