TUESDAY, Aug. 26 (HealthDay News) -- Women taking oral anticoagulants for five to seven months after an unprovoked venous thromboembolism may discontinue therapy if they have one or fewer risk factors for recurrent venous thromboembolism, according to a report published in the Aug. 26 issue of CMAJ, the journal of the Canadian Medical Association.

Marc A. Rodger, M.D., of the University of Ottawa in Ottawa, Ontario, Canada, and colleagues performed a multicenter, prospective cohort study of 600 patients to determine clinical predictors indicating low risk of recurrent venous thromboembolism. Patients with a first, unprovoked venous thromboembolism were enrolled over a four-year period and followed for a mean of 18 months.

During follow-up, 91 episodes of recurrent venous thromboembolism occurred after discontinuing oral anticoagulation therapy, the researchers report. While men had a 13.7 percent annual risk of recurrent venous thromboembolism, no combination of clinical predictors identified a low-risk subgroup of men, they found. Women with one or fewer of the following characteristics had a 1.6 percent risk of recurrent venous thromboembolism, while women with two or more risk factors had an annual risk of 14.1 percent: hyperpigmentation, edema or redness of either leg; positive D-dimer while taking warfarin; body mass index greater than or equal to 30; or age of 65 years or older.

"Women with zero or one risk factor may safely discontinue oral anticoagulant therapy after six months of therapy following a first unprovoked venous thromboembolism," the authors write. "This clinical decision rule identifies women with an annual risk of venous thromboembolism less than 3 percent who can likely safely discontinue anticoagulant therapy."

The study received funding from bioMerieux. Several authors of the study report financial relationships with the pharmaceutical industry.

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