A National Assessment of Warfarin Anticoagulation Therapy for Stroke Prevention in Atrial Fibrillation

Study Questions:

What is the status of anticoagulation care in routine practice outside of hospitals?


The investigators selected individuals with ≥2 months of international normalized ratio (INR) data, INR results of >1.2, and an INR diagnosis code of atrial fibrillation. Frequency of INR testing and time in the therapeutic range (TTR) were analyzed by age, sex, length of testing period, number of referred patients per provider, and median household income (based on home zip code). To assess the impact of risk factors on TTR, the authors applied a beta regression model with a probit link function using the ‘betareg’ open source statistical analysis package in R3.0.213.


The investigators identified 138,319 individuals referred by 37,939 physicians, yielding a total of 2,683,674 INR results. Patients had a mean age of 74 years; most (81%) were ≥65 years old and 55% were ≥75 years old. The mean TTR was 53.7% overall and improved with time on treatment, increasing from 47.6% for patients with <6 months of testing to 57.5% for those with ≥6 months (p < 0.0001). The number of patients tested per physician practice was positively associated with TTR. Younger age, female sex, and lower income were also independently associated with poorer anticoagulant control.


The authors concluded that there is widespread suboptimal anticoagulation control.


The present study reports suboptimal warfarin treatment for approximately one half of individuals with AF. Younger age, female sex, and lower income were independently associated with poorer anticoagulation control. Strategies to optimize stroke prevention for these populations are urgently needed. Potential approaches include implementation of processes shown to improve TTR and possible consideration of transitioning appropriate candidates to newer oral anticoagulants where appropriate.

Clinical Topics: Anticoagulation Management

Keywords: Stroke, Warfarin

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