Weekly INR Self-Testing Not Superior to Monthly Clinic Tests

Does not delay time to first stroke, major bleeding episode, or death to extent prior studies suggest
By Eric Metcalf
HealthDay Reporter

WEDNESDAY, Oct. 20 (HealthDay News) -- In patients using warfarin, self-testing of international normalized ratio (INR) doesn't appear superior to clinic testing for reducing the risk of adverse outcomes, including major bleeding and stroke, according to research published in the Oct. 21 issue of the New England Journal of Medicine.

David B. Matchar, M.D., of the Veterans Affairs Medical Center in Durham, N.C., and colleagues analyzed data from 2,922 individuals with mechanical heart valves or atrial fibrillation who used warfarin. Participants were randomized to weekly home self-testing of INR or monthly testing in a clinic. The primary end point was time to stroke, major bleeding episode, or death.

The researchers found that the self-testing group didn't have a significantly longer time to a first event. The groups also had similar rates of clinical outcomes, though the self-testing group had more minor bleeding episodes. Those in the self-testing group had a modest improvement in percentage of time with INR in the target range.

"In light of the poor record of usual care and the value of anticoagulation in preventing major events, we recommend that self-testing be considered for patients whose access to high-quality anticoagulation care is limited by disability, geographic distance, or other factors, if the alternative would be to withhold a highly effective treatment," the authors conclude.

Two co-authors disclosed financial relationships with a number of pharmaceutical and other companies.

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