Genetic Tests Can Reduce Risks From Blood Thinner Warfarin

Editor’s note: Pending an FDA decision, 23andMe no longer offers new customers access to health reports referred to in this post. Customers who purchased prior to November 22, 2013 will still be able to see their health reports, but those who purchased after that time will not. Those customers will have access to ancestry information as well as access to their uninterpreted raw data. Today at the American College of Cardiology conference in Atlanta, researchers from the Mayo Clinic and Medco Health Solutions, Inc., presented results showing that using genetic testing to guide dosing of the commonly used blood thinner warfarin reduces hospitalizations. Overall there were 31% fewer hospitalizations within six months of beginning warfarin therapy in those who received genetic testing compared to those who didn’t. A 28% drop in hospitalizations due specifically to bleeding or blood clots was seen. “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, in a press release.  “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.” Although a variety of factors influence a patient’s ideal dose of warfarin, variations in the CYP2C9 and VKORC1 genes play an important part.   The FDA has mandated that information about these variants be included in the labeling information of the medication since 2007.   In February of this year they updated the drug’s label to include specific dosage recommendations. Genetic testing before administration of warfarin, however, is not mandatory.   There has been significant disagreement over whether or not health outcomes are actually impacted when genetic information is available to physicians.   In fact, the Centers for Medicare and Medicaid Services, the federal agency that makes decisions about what Medicare, Medicaid and the Children’s Health Insurance Program will cover, decided last year that there was not sufficient evidence to justify covering genetic testing before warfarin administration for Medicare beneficiaries.  It will be interesting to see if the new study, which will soon be published in the Journal of the American College of Cardiology, will change this stance. has more on this story, including comments from researchers critical of the research.   The PowerPoint slides used in the researchers’ presentation are also available for download. (Free registration required) You can also read more here. 23andMe Health Edition and Complete Edition customers can view their data for genetic variations in the CYP2C9 and VKORC1 genes in the Warfarin (Coumadin ®) Sensitivity Drug Response Report. Only a physician can determine whether warfarin is the right medication for a particular patient and at what dosage it should be given.   The information contained in 23andMe Drug Response reports should not be used to independently establish a drug regimen, or abolish or adjust an existing course of treatment.