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Warfarin Response Testing: Medicare Calls for Feedback on Reimbursement

Posted Nov 19 2009 10:01pm

Guest post from Trisha Brown, MS, CGC, DNA Direct’s VP of Clinical Affairs:

FDA announced last year that the agency would update the label for the blood thinner warfarin to note that patients’ genetic makeup could strongly influence their response to the drug. Too high a dose of warfarin, and patients may experience uncontrolled bleeding—which can be fatal; too low, and patients risk developing life-threatening blood clots. Correct dosing is imperative for administering warfarin, which is the second most common drug, after insulin, implicated in emergency room visits for adverse drug events (1).

Now, the question is whether Medicare should cover the cost of genetic testing to identify the two genes that can affect patients’ reactions to warfarin. The outcome will be momentous and far-reaching: whatever the verdict from the Centers for Medicare & Medicaid Services (CMS), major private insurance companies are likely to follow suit. This week, CMS called for public comment on their decision.

Since FDA’s labeling change, there has been some debate among experts on using genotyping to prevent a significant number of adverse reactions to warfarin, or simply following the patient’s progress using a lab test that checks on how well the blood is clotting, called an INR (international normalized ratio) and adjusting accordingly. The latter view comes largely from thought leaders who work in major medical centers with distinct advantages: physicians can develop best practices; can use a single lab to assess the INR; and effectively communicate dosing changes and recommendations across a single healthcare team.

However, these centers hardly reflect the practices of the broader healthcare community. Most people who receive warfarin are not cared for by a gold-standard coagulation clinic. Variation between labs and point-of-care devices that measure INR can lead to significant and inappropriate changes in warfarin therapy (2). Also, adverse drug reactions to warfarin increase when patients see multiple physicians and visit more than one pharmacy (3) – as many do. Finally, warfarin is actually underused. Patients who could benefit from warfarin therapy are not getting it, sometimes because physicians may overestimate their individual risk, or are influenced by single past experience with an adverse drug reaction (4).

Genetic testing for patients who might receive warfarin can contribute on both sides: by helping healthcare providers target the best initial dose, it can significantly reduce the likelihood of adverse events, and genotyping could increase the appropriate usage of warfarin by giving physicians confidence in dosing.

DNA Direct believes in the power of consumer education. We have observed firsthand how information can help physicians and patients communicate and make informed choices, and this kind of communication is critical for warfarin dosing. Our personalized genotyping reports educate not just patients, but all members of the healthcare team, about warfarin dosing, genotyping and side effects, and provides guidance to talk to one’s family and physician about warfarin therapy. The reports are available directly to physicians or patients through DNA Direct or our lab partner, Iverson Genetics.

DNA Direct has recommended that the Centers for Medicare & Medicaid Services cover genotyping for initial warfarin dosing to allow individuals taking warfarin—especially those outside the care of a state-of-the-art coagulation clinic—the benefit of best initial dose, reduced adverse effects, and better therapeutic outcomes.

1. FDA Approves Updated Warfarin (Coumadin) Prescribing Information. Accessed September 4, 2008.2. Finck, KM et al. Am J Heal Sys Pharm (2001) 58:684-688
3. Metlay, JP et al J Gen Intern Med (2008) epub ahead of print doi:10.1007/s11606-008-0708
4. Choudrey, NK et al BMJ (2006) 332;141-145

This entry was posted on Friday, September 5th, 2008 at 3:27 pm and is filed under Drug Response, Privacy, Legislation & Policy. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

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