Agency News and Notes

AHRQ report finds value of genetic testing for preventing blood clots unproven

There is insufficient evidence to conclude that genetic testing for two gene mutations in adults with a history of blood clots helps to prevent a condition known as deep-vein thrombosis or to improve other clinical outcomes, concludes a new report by the Agency for Healthcare Research and Quality (AHRQ). The report also failed to find any benefit from genetic testing of family members of patients who have at least one of the two mutations — known as Factor V Leiden (FVL) and prothrombin G20210A—as well as a history of deep-vein thrombosis. As many as 600,000 Americans each year may have deep-vein thrombosis—blood clots that form in the legs or pelvis. These clots can travel to the lungs (pulmonary embolism), which is sometimes fatal.

Deep-vein thrombosis occurs most commonly in people who are sedentary for a long period of time, such as when recovering from surgery or traveling long distances. The report, Outcomes of Genetic Testing in Adults with a History of Venous Thromboembolism, was authored by Jodi Segal, M.D., and colleagues at the AHRQ-supported Johns Hopkins Evidence-based Practice Center in Baltimore. The authors failed to find any studies that directly addressed the effect of genetic testing on patient outcomes. However, they did find research indicating that keeping patients who have a genetic tendency to develop blood clots on blood-thinning drugs such as warfarin reduced the chance of a future clot.

This benefit appears to be similar to that seen in patients who do not have the genetic tendency to develop blood clots, but who have a history of clots. AHRQ's evidence report is available at http://www.ahrq.gov/clinic/tp/fvltp.htm.

For more AHRQ information on deep-vein thrombosis, see Preventing Hospital-Acquired Venous Thromboembolism: A Guide for Effective Quality Improvement, at http://www.ahrq.gov/qual/vtguide/ and Your Guide to Preventing and Treating Blood Clots, available in both English and Spanish at http://www.ahrq.gov/consumer/bloodclots.htm.

Free, single copies of all AHRQ publications are available from the AHRQ Publications Clearinghouse.

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