TUESDAY, March 16 (HealthDay News) -- A simple genetic test that helps doctors determine the best dose of the blood-thinner drug warfarin for individual patients could reduce hospitalizations by one-third during the early dose-adjustment phase, a new study has found.

The test identifies variations in two genes that strongly influence sensitivity to warfarin (Coumadin), which is used to prevent blood clots in people with high-risk conditions, such as atrial fibrillation, or after surgery to replace a heart valve.

"Genetic testing is a tool clinicians can use to more accurately predict the best warfarin dose early on," Dr. Robert S. Epstein, chief medical officer and president of the Medco Research Institute in Franklin Lakes, N.J., said in a news release from the American College of Cardiology. "Patients may get to a stable dose more quickly and, therefore, have a lower risk of negative outcomes, such as excess bleeding or unwanted blood clotting."

The findings were to be presented Tuesday at the college's annual meeting in Atlanta.

The study included 896 people who, shortly after beginning warfarin therapy, gave a blood sample or cheek swab that was analyzed for expression of two genes -- CYP2C9 and VKORC1 -- that revealed sensitivity to warfarin. People with high sensitivity were put on a reduced dose of warfarin and had frequent blood tests. People with low sensitivity were given a higher dose of warfarin.

During the first six months that they took warfarin, those who underwent genetic testing were 31 percent less likely to be hospitalized for any reason and 29 percent less likely to be hospitalized for bleeding or thromboembolism than were a group that did not have genetic testing.

Epstein said that the cost of the genetic testing -- $250 to $400 -- would be justified by reduced hospitalization costs.

"If we reduce just two hospitalizations per 100 patients tested, that more than compensates for the cost of genotyping," he said.

More information

The U.S. Agency for Healthcare Research and Quality explains the safe use of blood thinners.