Harvard Heart Letter

Heart Beat: Too soon to sell a gene test for warfarin?

Heart Beat

Too soon to sell a gene test for warfarin?

One of the frustrations of starting warfarin (Coumadin) to prevent blood clots is finding the amount that's right for you. It can take several weeks of trial and error to settle on a daily dose that inhibits your blood's clotting cascade just enough to prevent clots from forming and not so much that you bleed too easily.

The discovery that two key genes influence how quickly the body breaks down and eliminates warfarin has prompted the development of genetic tests that may "" we stress the "may" "" simplify the process of finding the safest warfarin dose. One company, Genelex, is already marketing a test directly to consumers that it claims will help you reach your target dosage "faster and safer."

Although the concept makes sense, there are no large trials showing that genetic testing speeds the process of finding the right warfarin dose, helps maintain the right dose, or improves the safety or effectiveness of warfarin, says Dr. Samuel Z. Goldhaber, an anticoagulation specialist and professor of medicine at Harvard Medical School. To fill that void, he is leading a trial at five Harvard-affiliated hospitals that incorporates rapid-turnaround genetic testing for people just starting warfarin therapy.

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