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Doctor, Patient Adoption of PGx Testing Increases in PBM-Initiated Programs, Medco Reports at ASHG


Originally published Nov. 9.

By Turna Ray

Education and no cost concerns increase the likelihood that doctors and patients will consent to pharmacogenetic testing for warfarin and tamoxifen, according to a two-year study conducted by the Medco Research Institute.

The study, presented last week at the American Society for Human Genetics annual meeting, found that when doctors and their patients were educated about PGx-guided dosing for these two drugs, about half of more than 40,000 patients identified for the study received testing. The participating patients’ prescription drug benefit plan covered the full cost of the service and genetic tests for the study.

Medco said that these results are 45 times higher for warfarin testing and seven times higher for tamoxifen testing than when testing is conducted outside the PBM program.

Medco began studying the utility of PGx-guided dosing for warfarin and tamoxifen several years ago. Last year the pharmacy-benefit manager launched Genetics for Generics, a program through which the company offers PGx testing for generic drugs to its customers in order to lower costs and increase efficiency in the healthcare system. This summer, Medco extended its personalized medicine program as an option for all its customers and added new drugs for which it is offering genetic testing (PGx Reporter 05/26/10).

Before Medco implemented its pharmacy-based personalized medicine program, it conducted a benchmark analysis with the US Food and Drug Administration to assess how much PGx testing was being conducted by doctors. At the time, Medco found that only 1.7 percent of patients received genetic testing for warfarin and 2.3 percent of those on tamoxifen received genetic testing as part of clinical care.

"While the potential for broader uptake of pharmacogenomic testing exists, little is known about the effectiveness of systems and processes that are designed to make wider adoption of these tests possible," Medco wrote in an abstract outlining the study findings. "This study was conducted to examine the early impact a novel pharmacy-based approach utilizing the unique position and capabilities of a national pharmacy benefit manager would have on the adoption of pharmacogenomic testing."

Beginning in mid-2008, Medco identified study participants on warfarin or tamoxifen by sifting through claims data for patients whose benefit provider is enrolled in its personalized medicine program. Medco then contacted the patients' doctors to let them know the availability of a genetic test that might improve the safety and efficacy of the treatments. After getting the doctors' consent, Medco reached out to the patients and let them know about the availability of testing. If the patients consented, then Medco obtained DNA samples from them through a self-collection process, analyzed the samples through a national lab partner, and communicated the results to doctors.

More than 4,000 doctors, around 58 percent of them operating in the primary care setting, came on board to gauge which of their patients were appropriate to receive genetic testing before administering warfarin. Around 1,500 physicians, 63 percent of them oncologists, agreed to consider their patients for genetic testing ahead of tamoxifen treatment.

According to Eric Stanek, Medco’s senior director of personalized medicine research and the study leader, Medco provided one-on-one education to doctors through faxes, telephone discussions, and the Web. Medco's specialist pharmacists also answered physicians' questions about testing.

Participating doctors applied their own clinical criteria to make their decisions about testing patients. "For warfarin patients, physicians considered issues such as whether the patient was on short-term versus long-term therapy and also if the patient had been on warfarin before and they were already aware of the optimal dose for that patient," Stanek told PGx Reporter. "For tamoxifen, the decision to test was influenced by the patient’s menopausal status, which affects which alternatives to tamoxifen therapy exist should the patient be discovered to be a poor metabolizer."

Through this pharmacy-initiated education and testing, physicians gave their consent for testing in 49 percent of their patients using warfarin, and for 54 percent of their patients using tamoxifen. On the patient side, 39 percent of patients eligible to receive CYP2C9/VKORC1 testing for warfarin agreed to get tested, and 56 percent agreed to CYP2D6 testing for tamoxifen.

Those patients, who after learning about the tests, still did not agree to getting genetically tested, had a variety reasons for their decision. "When reasons were provided by the patient, they indicated declining for reasons such as simply wanting an additional test done, or that they were planning to discontinue the medication in question sometime soon," Stanek said. Sometimes, patients gave no specific reason at all, he added.

Two years ago, before PBMs initiated personalized medicine programs such as those available now through Medco and CVS Caremark, the situation was quite different. A 2008 survey conducted by Medco and the American Medical Association found that most physicians recognized that genes play a role in patient drug response, but at the time, they felt they needed more training before they could prescribe such tests to guide treatment decisions.

"The substantial rise in the chances of a patient on either warfarin or tamoxifen receiving genetic testing clearly demonstrates that this pharmacy-based approach is an effective model for increasing adoption of pharmacogenomic testing in routine clinical practice on a national scale," Medco concluded in the abstract. "Further, it affirms that providing choice, convenient processes, access, and information to patients and physicians alike is key to attaining high rates of consent for genetic testing."

Garnering genetic testing through a PBM-initiated program increases the chances that tests for warfarin sensitivity and tamoxifen response will be reimbursed by insurers; the fact that the cost of care and tests was not a factor in Medco's study certainly could have impacted doctors' and patients' willingness to agree to testing.

Outside PBM personalized care programs, genetic tests to guide administration of warfarin and tamoxifen are not readily covered by insurers. Payors have said these interventions currently lack the evidence needed for coverage showing that such tests are medically necessary and improve outcomes over standard methods.

Addressing this point, Stanek said that Medco did not look at whether test adoption would have been impacted by different coverage conditions. "Though in a way, our observed increase in testing compared to the rates without intervention demonstrates that knowledge of coverage plus access to the test works well," Stanek said via e-mail.

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