Expanding the testing panel had a major impact on efficacy. Results reported by her group at the AHA meeting last November showed that immediately following the start of warfarin treatment the percentage of INR levels that fell out of the therapeutic range was 42%, a statistically significant improvement over the 65% rate seen in 308 historic controls drawn from the year immediately preceding the start of routine genotyping (Circulation 2014;130A:16119). The results showed that the average number of days for patients to reach their first INR measurement in the therapeutic range fell from 11 days prior to genotyping to 4 days, and the average number of days needed on treatment with low-molecular-weight heparin, a bridging strategy until a therapeutic INR is achieved, fell from 10 days among the historic controls to an average of 2 days. The between-group differences for all three of these metrics reached statistical significance in analyses that adjusted for multiple variables, and that used propensity scoring, Dr. Cavallari said.But although genotyping prior to starting warfarin “is available and reasonable to use, until Medicare starts paying for it, doing this will be hard to implement,” Dr. Cavallari conceded during a November talk. Although warfarin-oriented genetic testing may be performed routinely at the University of Illinois, a lot of clinicians elsewhere are holding back, in part because of reimbursement issues and in part because “they want to see proof of better patient outcomes,” said Pharm.D., a cardiovascular pharmacology researcher at the University of Connecticut in Storrs. Like many who look at the evidence for routine genetic testing in cardiovcascular medicine, they “want to see differences in hard clinical outcomes before incorporating it into their practices,” Dr. Baker said.
Dr. Hershberger, Dr. Mestroni, Dr. Ware, Dr. Seidman, Dr. Tybjaerg-Hansen, and Dr. Cavallari had no disclosures. Dr. Shuldiner is an employee of Regeneron. Dr. Mega has been a consultant to Janssen, Boehinger Ingelheim, American Genomics, Bayer, and Portola, and has received research grants from eight companies. Dr. Baker received a research grant from Gilead.
On Twitter @mitchelzoler