Between 5 percent and 13 percent of those having recurrent clots die because of them, he added.
Before doctors can start telling women who meet the criterion that they can stop taking Coumadin, Rodger said, "This needs to be validated in a second study which we are currently planning." Those plans call for enrolling 3,000 people in 40 medical centers in Canada, the United States and four other countries.
"The study will take about two years to recruit patients and will have a one-year follow-up, so results are expected in three years," he said.
Dr. Clive Kearon is a professor of medicine at McMaster University's Michael G. DeGroote School of Medicine, in Hamilton, Ontario, Canada, who wrote an accompanying editorial in the journal. "One would be happy to be able to recommend stopping" blood-thinning therapy, he said, because it increases the risk of major bleeding. "The current recommendation is to remain on long-term therapy, but many patients elect not to do it."
Coumadin is a difficult drug to manage, requiring frequent blood tests and even careful dieting, since green, leafy vegetables are rich in vitamin K, which governs blood clotting.
Some doctors might not wait for the three years needed to get confirmation of the finding, Rodger said. "Oftentimes, patients choose not to take an anticoagulant [blood thinner]," he said. "So, a physician might feel more comfortable to allow women with one or fewer of these risk factors to discontinue the medication."
Learn more about venous thrombosis from the U.S. National Library of Medicine.
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