Harvard Heart Letter

Heart beat: Trial gives nod to home warfarin monitoring

Heart beat

Trial gives nod to home warfarin monitoring

Warfarin (Coumadin, generic) is a Goldilocks drug. Take too little, and stroke-causing clots can form in the bloodstream. Take too much, and bleeding into the stomach or brain can occur. Getting the dose just right requires routine blood tests, which usually means schlepping to a doctor's office, clinic, or lab every month. Would weekly self-testing at home be better, the same, or worse than having it done "professionally?" That was the question The Home INR Study (THINRS) aimed to answer.

THINRS included nearly 3,000 veterans who were taking warfarin because they had a mechanical heart valve or atrial fibrillation. Half had a monthly blood test to check their international normalized ratio (INR), which measures how quickly the blood clots. The other half were given home INR meters and asked to test their blood once a week. After an average of three years, there were slightly fewer strokes, major bleeding episodes, or deaths in the home testing group. The home testers were in the right INR range more often than the clinic testers. They were also more satisfied with their monitoring. The results were presented at the American Heart Association's annual meeting.

Some doctors aren't convinced that home testing is safe and effective. The results of THINRS and several previous studies show that it is. Others aren't aware that home INR testing is available. It is — and is usually covered by insurance — although you generally have to do it through independent services like Philips INR@Home, Quality Assured Services, ATS Medical, and others. More information about home INR monitoring is available at health.harvard.edu/141.

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