Mar 17 2010
Hospitalization rates for heart patients taking warfarin, the world's most-prescribed blood thinner, dropped by approximately 30 percent when genetic information was available to doctors prescribing the drug, researchers from Medco Health Solutions, Inc.-- in association with the Medco Research Institute™ -- and Mayo Clinic announced today. Results of the first nationwide prospective study examining outcomes when incorporating genetic testing into the management of warfarin as part of the usual care of patients were presented today at the American College of Cardiology's 59th annual scientific session and will be published in the Journal of the American College of Cardiology.
Warfarin, marketed under the brand names Coumadin® and Jantoven®, is a blood thinner that is exceptionally difficult to properly dose because the two million patients starting the drug annually have widely varying responses to the medicine due to a variety of factors including genetics. It is estimated that up to 20 percent or more of patients can be hospitalized for bleeding within six months of starting on the drug. This comparative effectiveness study, conducted in national "real world" settings, validates that testing for an individual's unique genetic predisposition can significantly improve warfarin's safety and effectiveness by providing information about the patient's sensitivity to the drug.
Warfarin is the leading cause of drug-related emergency room visits among the elderly. Accordingly, the FDA requires a so-called "black-box warning" on warfarin labels describing the bleeding risk and recommending 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.
"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 Dr. Robert S. Epstein, 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 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, PhD, at Mayo Clinic's Department of Laboratory Medicine and Pathology and co-author of the study.
Reduced hospitalization risk
The study revealed 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 to determine how sensitive they may be to the drug.
The study included patients from 49 states who were insured by 29 different health plan sponsors all managed by Medco and were being treated in a variety of medical settings. It 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 drawn from the same participating plan sponsors the year prior who were taking warfarin but had not received a genetic test.
"Our health plan sponsors recognize the importance of genetic testing in improving patient outcomes and avoiding medical costs due to adverse drug events," said Dr. 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."
The study, which started in July 2007, relied upon Medco's integrated medical and pharmacy claims systems and included patients aged 40-75 who were initiating warfarin therapy anywhere in the country for any reason and prescribed by any physician. The average age of the patients in the study was 65 and males represented about 60 percent of both the study and control groups. DNA samples obtained from either blood cells or buccal cells (cotton swab scraped inside the cheek) were analyzed by Mayo Clinic to supply physicians with genetic 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.
Warfarin: Old drug with genetic link
Warfarin, which is sold by generic drug manufacturers and distributors, and under the brand name Coumadin by Bristol Myers Squibb and under the brand name Jantoven® by Upsher-Smith, is used to reduce the risk of death, heart attack or stroke after a patient has a heart attack. It is also used to treat and prevent venous thrombosis (blood clots), pulmonary embolism, and thromboembolism associated with atrial fibrillation or heart valve replacement surgery. The drug has been available as a medication for more than 50 years, but warfarin therapy requires regular patient monitoring because of its narrow therapeutic range, meaning that the dose needed to obtain a therapeutic effect is very close to the dose that can cause serious adverse events. Genetic testing offers an additional opportunity to help clinicians reach a more precise dose for patients.
SOURCE Medco Health Solutions, Inc.
Decoding the genetic roots of stroke and heart attack