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Warfarin Genetic Test Not Cost Effective for Initial Dosing

NEW YORK (GenomeWeb News) – Genetic testing for initial warfarin dosing is not cost effective for most patients, according to research appearing online today in the Annals of Internal Medicine. Instead, the study suggested, such tests may be more suitable for those at high risk of hemorrhaging.

Warfarin is commonly prescribed to prevent blood clotting. But because the drug can cause serious bleeding in some patients, care must be taken in warfarin dosing. Several studies suggest that variants in genes such as cytochrome P450 CYP2C9 or vitamin K epoxide reductase (VKORC1) influence warfarin’s effect in the body and should be considered before warfarin dosing to prevent bleeding events.

The US Food and Drug Administration changed warfarin’s labeling in 2007 to reflect such findings. Now, physicians are urged to consider genetic testing prior to treating an individual with warfarin.

But when researchers measured the cost effectiveness of such genetic testing, they found that the tests were only cost effective in a specific high-risk group. The team looked at the cost effectiveness of genotyping patients with nonvalvular atrial fibrillation, a type of heart arrhythmia, before initial warfarin dosing using data from three published studies.

Their results suggest that genetic testing can improve patient outcomes. But the cost was high. Based on the researchers’ statistical models, each quality-adjusted life year gained cost more than $170,000. Using available data and a test cost of $400 (in 2007 dollars), the researchers found that there was only about a 10 percent chance that warfarin genetic tests were cost effective.

The team’s analyses indicated that the genetic tests would only dip below $50,000 per quality-adjusted life year gained if it were restricted to those at high hemorrhage risk. Alternatively, they noted, testing would be cost effective if it prevented at least a third of all major bleeding, were available within 24 hours, and cost less than $200.

That would require low-cost tests that could be done in house, the study’s lead author Mark Eckman, a medical researcher at the University of Cincinnati, said in a statement. He said most tests are currently sent to outside labs.

"Personalized, predictive medicine offers great promise, but we need to carefully examine benefits and understand the cost-effectiveness of such strategies before we spend a lot of money on very expensive tests," Eckman said.

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