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CVS study examines genetic testing impact on cardiovascular prescribing
November 13th, 2013
WOONSOCKET, R.I. – A new study by researchers at CVS Caremark Corp. and Brigham and Women's Hospital showed that a genetic marker for improving medication safety is underused in prescribing for cardiovascular treatments.
CVS said Wednesday that the study, published in the November issue of the American Heart Association journal Circulation: Cardiovascular Quality and Outcomes, found that only one in five patients who tested as poor metabolizers of the blood thinner clopidogrel had their antiplatelet therapy changed as recommended by the Food and Drug Administration.
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 about the rapidly evolving body of evidence for pharmacogenomics, according to CVS.
"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," stud co-author Troy Brennan, executive vice president and chief medical officer at CVS Caremark, said in a statement. "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 (ACS) or percutaneous coronary intervention (PCI) 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, CVS said, adding that 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 about a third of patients identified as being poor drug metabolizers. Though the patients who underwent genetic testing were much more likely to have their antiplatelet regimen changed compared with patients who didn't 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," stated the study's senior investigator, Niteesh Choudhry, associate physician in the division of pharmacoepidemiology and pharmacoeconomics at Brigham and Women's Hospital and associate professor at Harvard Medical School. "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."