Finding May Allow Some Women to Stop Blood Thinners

MONDAY, Aug. 25 (HealthDay News) -- A new study identifies some women -- but not men -- who might be able to stop taking blood-thinning medication for the clotting condition called venous thromboembolism.

Current guidelines call for indefinite use of a clot-preventing drug, most often warfarin (Coumadin), for many people with the condition. But researchers report that they've identified a group of traits in women that indicate a very low risk of recurrent clots, so that medication might not be necessary after a few months.

The study, published in the Aug. 26 issue of the Canadian Medical Association Journal, found no such indicators of low risk in men with the condition.

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The finding applies to what Dr. Marc A. Rodger, a senior scientist at the Ottawa Hearth Research Institute, who led the study, called "out-of-the-blue" venous thrombosis, with no obvious cause of clots in the legs, arms or lungs. In cases where there is a known cause, such as surgery, the risk of a recurrent clot is low and anti-clotting therapy is routinely stopped after a matter of months.

Rodger and his colleagues studied 69 potential predictive factors in more than 600 men and women who had stopped taking an anticoagulant after a first venous thromboembolism. They singled out four of those factors: discoloration, redness or swelling of a leg; high levels of a blood clotting marker, D-dimer; obesity, marked by a body mass index of 30 or higher; and being 65 or older.

Women who had one or none of those factors had a 1.6 percent chance of developing another clot in the next year. Women with two or more had a 14.1 percent one-year risk.

It's a "bit of a mystery" why no predictive factors were found for men, Rodger said. "There are theories about hormonal differences, but none has been proved," he said.

What is known is that while men and women are at equal risk of a first out-of-the-blue venous thrombosis, men are at 1.5 to 2 times the risk of a recurrence, Rodger said. "It's been documented in several studies that men are at increased risk of recurrence," he said.