Genetic testing may provide more accurate warfarin dose, lower risk of bleeding and clots

Physicians who check the DNA of patients before initiating warfarin therapy are more likely to provide the correct dose, avoiding the possibility of readmittance to a hospital, according to a new study presented in March at the American College of Cardiology’s 59th annual scientific session.

About 2 million Americans are annually prescribed warfarin to treat or prevent venous thrombosis, pulmonary embolism, and thromboembolism associated with atrial fibrillation or heart valve replacement surgery. It also reduces the risk of death, heart attack, and stroke after a heart attack. Too much warfarin can lead to bleeding, too little can lead to clots, and either dose can kill. Up to 20% of patients are hospitalized within their first 6 months on the drug.

Several companies sell tests for the 2 genes that control how warfarin is metabolized. But the tests are expensive-in the range of $250 to $400- and a dose of warfarin costs less than $6 a month.

According to the study, paid for by Medco Health Solutions Inc., patients given genetic tests to set their initial warfarin dose had about a 30% lower risk of being hospitalized than similar patients whose doses were set by the physician without the use of a genetic test.“If we reduce just two hospitalizations per 100 patients tested, that more than compensates for the cost,” said Robert Epstein, MD, the study’s leader and chief medical officer of New Jersey-based Medco.

For the study, researchers at the Mayo Clinic analyzed genetic tests on cells from cheek swabs of 896 patients in Medco plans who had started warfarin therapy. Each patient’s physician was given the results and advice on how to interpret them to set a dose.For a comparison group, researchers selected 2,688 similar patients from the same insurance plans who were also starting on warfarin and whose initial dose was set by the physician without the use of the genetic test information.

After 6 months, 18% of the gene-tested patients and 26% of the others had been hospitalized - about a 30% lower risk for those given genetic testing.

Formulary Editorial Advisory Board Member Michele B. Kaufman, PharmD, a clinical pharmacist at New York Downtown Hospital in New York City and president & CEO of PRN Communications Inc., said decreasing bleeds and clots in warfarin users by using genetic testing is a great way to utilize evidence to improve outcomes.

“Pharmacogenomics has the potential to have a very large impact on patient management but must be done in a way that is universally accepted by insurers and appropriately utilized by providers,” Dr Kaufman cautioned. “Educating healthcare providers to know when to utilize these tests for diagnosing patients, recommending treatments, as well as monitoring and follow-up, needs to occur.”