CVS Caremark study: More education needed on genetic testing in prescribing antiplatelet drugs

WOONSOCKET, R.I. — A new study conducted by researchers at CVS Caremark and Brigham and Women's Hospital explored the impact of genetic testing on prescribing patterns for cardiovascular therapy and found that there is an opportunity to improve upon the information physicians and patients receive on the evolving body of evidence for pharmacogenomics.

The study, published in the November issue of the American Heart Association journal Circulation: Cardiovascular Quality and Outcomes, found that only 1-out-of-5 patients who tested as poor metabolizers of the blood thinner clopidogrel had their antiplatelet therapy changed as recommended by the FDA. In addition, the study found that prescribers declined genetic testing in 25% of cases evaluated, while less than 10% of patients who were directly offered the genetic evaluation declined testing. The researchers concluded that the prescribing patterns noted in the study likely reflect the unclear impact and physician uncertainty regarding the evidence for pharmacogenomics.

"We're entering an age when we can begin to create tailored treatment regimens for individual patients, but a genetic test is only valuable when providers and their patients can understand and act on the results," Troyen A. Brennan, EVP and chief medical officer of CVS Caremark and a study co-author, said. "This research shows there is an opportunity to improve upon the information doctors and patients receive on this evolving topic so that they can make the best treatment decisions."

The study examined prescribing patterns for patients with recent acute coronary syndrome or percutaneous coronary intervention who were prescribed the antiplatelet medication clopidogrel. While clopidogrel has been shown to reduce the risk of major adverse cardiovascular events for these patients, there is significant variability in how individual patients respond to the drug. In fact, patients who are poor metabolizers of clopidogrel may have reduced therapeutic benefit and a higher risk of adverse cardiovascular events. The FDA has advised avoiding the use of clopidogrel in patients who are poor metabolizers and recently modified the boxed warning to advise health care professionals to consider the use of other antiplatelet medications or alternative dosing strategies for poor metabolizers.

Health care providers were offered access to a genetic test as part of the patient's health benefit to identify the patient's ability to metabolize clopidogrel. Nearly 500 patients completed the test, with approximately one-third of patients identified as being poor drug metabolizers. While the patients who underwent genetic testing were significantly more likely to have their antiplatelet regimen changed as compared with patients who did not undergo testing, only 20.5% of patients identified as being poor metabolizers had their antiplatelet therapy intensified or changed to another drug.

"In this study, about half of the providers that were contacted about the availability of a genetic testing benefit did not respond at all, and among those who did decide to use the test, the vast majority of patients identified as poor metabolizers did not have a change in therapy despite FDA warnings suggesting that they should," added Niteesh K. Choudhry, associate physician, Division of Pharmacoepidemiology and Pharmacoeconomics, Brigham and Women's Hospital, associate professor, Harvard Medical School and the study's senior investigator. "While there is significant uncertainty about how clinician's should respond to the results of genetic testing for antiplatelet drugs, this study clearly shows that patients and their doctors need more guidance and education about how best to apply these results to improve patient outcomes."