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New Test Identifies Blood Clot Risk

Could help spot people in need of blood-thinning therapy, study says

TUESDAY, July 25, 2006 (HealthDay News) -- A new test could help identify which people who have had one blood clot in a vein will be at risk of another one.

The discovery could help low-risk individuals avoid anticoagulant therapy, which can produce serious side effects, while ensuring that high-risk patients who need the treatments get them, researchers are reporting.

Anticoagulant treatment for patients with venous thromboembolism -- the formation of blood clots, typically involving the deep veins of the legs or the lungs -- consists of the blood-thinner heparin followed by vitamin K antagonists for at least three to six months.

But even then, one-third of the patients will have a clot recurrence within five to eight years, and about 5 percent of these will be fatal, the researchers said.

The study is published in the July 26 issue of the Journal of the American Medical Association.

In their study, Dr. Gregor Hron and his colleagues at Medical University of Vienna, Austria, determined that by measuring the production of thrombin -- a protein in blood that causes clotting -- patients could be classified as "high risk" and "low risk" for recurrence of venous thromboembolism.

Nine hundred and fourteen patients with initial venous thromboembolism -- vein clots -- were followed for an average of 47 months after they discontinued vitamin K antagonist therapy; 100 of them suffered a second clot.

The researchers found that two-thirds of the patients had low thrombin generation and a 60 percent reduced risk of developing a new clot, compared with one-third of the patients with high thrombin generation.

"Using a simple, commercially available laboratory method developed to measure thrombin generation, we were able to identify patients in whom the long-term risk of recurrent venous thromboembolism is almost negligible," the authors wrote.

"Considering the incidence rates of severe or fatal hemorrhage related to anticoagulant therapy and the case fatality rate of recurrent venous thromboembolism, patients with low peak thrombin generation would almost certainly not benefit from indefinite anticoagulant therapy. Consequently, extensive thrombophilia screening appears to be unnecessary in this large, low-risk patient group," the researchers concluded.

One expert called the study intriguing but questioned the methods used by the researchers.

"This well-respected research group from Vienna has asked one of the most important questions regarding long-term management of deep venous thromboembolism and pulmonary embolism: Can a simple blood test predict recurrence after discontinuing anticoagulation? The answer appears to be 'yes,' " said Dr. Samuel Goldhaber, director of the venous thromboembolism research group at Brigham and Women's Hospital, in Boston.

"However, the only problem is that the blood test was not performed until 13 months after stopping anticoagulation, rather than being used at the time a decision was being made whether to continue anticoagulation. Nevertheless, the findings are intriguing and important," he said.

Another expert said there are already tests that predict the recurrence of venous thromboembolism.

The finding is not new, said Dr. Jack E. Ansell, a professor of medicine at Boston University School of Medicine. "We already have one test that has been shown to predict recurrence -- the D-dimer assay," he said. "An elevated D-dimer after discontinuing anticoagulation will predict recurrence."

"The D-dimer assay is widely available and is used today by many physicians as a risk index for recurrent venous thromboembolism," he added.

More information

The University of Michigan can tell you more about deep vein thrombosis.

SOURCES: Jack E. Ansell, M.D., professor, medicine, Boston University School of Medicine; Samuel Goldhaber, M.D., director, venous thromboembolism research group, Brigham and Women's Hospital, Boston; July 26, 2006, Journal of the American Medical Association
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