Study Launched to Assess Impact of Genetic Testing in Warfarin Dosing


March 1, 2011

March 1, 2011 – A new study assessing the utility of genetic testing to determine a personalized warfarin dose for individual patients has begun at Overlake Hospital Medical Center in Bellevue, Wash. The WARFARIN Study will help determine if genetic testing can reduce a patient’s risk of serious bleeding or clotting events. It will use a test developed by Iverson Genetic Diagnostics.

Warfarin, the most commonly prescribed blood thinner worldwide, causes up to 100,000 serious and unnecessary adverse events every year, including thousands of deaths. Studies have shown that DNA testing can dramatically improve the safety and effectiveness of warfarin, with estimated savings to the U.S. healthcare system of approximately $1.1 billion.

Warfarin is difficult to dose as patients respond to it differently according to their genetic makeup. Too much can result in severe bleeding, and too little can cause clot formation and increased risk of stroke. In the past, warfarin dosing relied on trial-and-error, which exposed patients to serious medical risks. Warfarin is the second most frequent cause of drug-related emergency room visits.

"Safeguarding the health of our citizens is always a top priority of government," said Rogers Weed, director of the Washington State Department of Commerce. "The WARFARIN Study aims to demonstrate that using genetic testing for warfarin dosing can improve patients' overall health, save lives and lower healthcare costs here in Washington as well as nationwide."

Over the past few years, two genetic variants have been identified that predict an individual's response to warfarin. Using genetic testing to guide physicians in starting warfarin therapy could reduce deaths, increase overall patient safety and lower national healthcare system costs. Given the magnitude of these potential improvements in warfarin use, the Centers for Medicare & Medicaid Services (CMS) has authorized the study to gather data on the potential value of a pharmacogenetic test.

Researchers have identified two specific genes, VKORC1 (for warfarin sensitivity) and CYP2C9 (for warfarin metabolism), which contribute up to 40 percent of individual patient variations in response to using warfarin. The study will assess the extent to which serious adverse events – hemorrhage and clotting – can be avoided when warfarin dosing is guided by genetic testing for these two genes. Results will be compared to warfarin dosing calculated without these pharmacogenetic data.

The 18-month study will determine patients' rates of warfarin-related adverse events at 30, 60 and 90 days from initial warfarin dosing. Study results will be used by CMS for reimbursement decision-making. The multicenter, randomized, blinded, parallel-group study is being led by Principal Investigator Elizabeth Ofili, M.D., chief of cardiology, director of clinical research, and associate dean for clinical research at Morehouse School of Medicine.

"This landmark study is about more than warfarin," said Dean Sproles, CEO and chairman, Iverson Genetic Diagnostics, which initiated the WARFARIN Study. "It is about individualizing treatment to improve patient safety and outcomes, thereby reducing healthcare costs.”

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