ATLANTA – A simple genetic test can reduce hospitalization rates by almost a third for heart patients taking warfarin, the world's most-prescribed blood thinner, according to a study released today by researchers from Medco Health Solutions, Inc. (in association with the Medco Research Institute) and the Mayo Clinic.

Announced at American College of Cardiology's 59th annual scientific session, and due to be published in the Journal of the American College of Cardiology, it is the first nationwide prospective study examining outcomes when incorporating genetic testing into the management of warfarin as part of the usual care of patients.

Warfarin, which is marketed under the brand names Coumadin and Jantoven, is a blood thinner that is exceptionally difficult to properly dose: The two million patients who start the drug each year have widely varying responses to the medicine due to a variety of factors – including genetics. It's estimated that perhaps 20 percent of patients are hospitalized for bleeding within six months of starting the drug.

The comparative effectiveness study, conducted in nationwide "real world" settings, found that testing for a patient's unique genetic predisposition can significantly improve warfarin's safety and effectiveness by providing information about the patient's sensitivity to the drug, revealing that patients whose therapy included genetic testing were 31 percent less likely to be hospitalized for any cause, and 28 percent less likely to be hospitalized for a bleeding episode or thromboembolism when compared to patients using the blood thinner without genetic testing.

"Warfarin represents an excellent example of how to take the modern science of genetic testing and apply it to making an older drug more effective and safer to use," said Robert S. Epstein, MD, lead author of the study and Medco's chief medical officer and president of the Medco Research Institute. "These results show that we can greatly reduce hospitalizations, and their significant costs, by making genetic testing routine early in a patient's therapy with warfarin."

The Food and Drug Administration requires a so-called "black-box warning" on warfarin – the leading cause of drug-related emergency room visits among the elderly – that describes the bleeding risk and recommends regular monitoring to ensure the patient is responding properly to the dose. The FDA recently approved a labeling change that provides dose recommendations based on genetic test results.
  
"The test provides the information a physician needs to more precisely dose a patient so that an individual who has a low sensitivity to the drug can be dosed higher to minimize the risk of stroke and someone who is highly sensitive to the drug can be given a lower dose to avoid bleeding," said Thomas P. Moyer at Mayo Clinic's Department of Laboratory Medicine and Pathology and co-author of the study.

The study, which began in July 2007,  compared the hospitalization rates of 896 patients who were given the genetic test early in their warfarin therapy to a control group of 2,688 patients who were taking warfarin but had not received a genetic test.

DNA samples were obtained and blood cells or buccal cells and were analyzed by Mayo Clinic, giving doctors information pertaining to the CYP2C9 and VKORC1 genes, which affect patient response to the drug. Mayo Clinic reports provided doctors with information on how to interpret the results and apply them to drug management decisions. Medical claims were used to compare hospitalization rates between the group receiving the genetic test and those who did not.

"Our health plan sponsors recognize the importance of genetic testing in improving patient outcomes and avoiding medical costs due to adverse drug events," said Epstein.  "If it costs a few hundred dollars for the genetic test but avoids the $13,500 hospital bill, it very quickly pays for itself."