Gene Test for Dosage of Warfarin Is Rebuffed
nytimes.com
By ANDREW POLLACK
In a setback for the fledgling field of personalized medicine, Medicare has decided not to pay for genetic tests intended to help doctors determine the best dose of the blood thinner warfarin for a particular patient.
In a proposed decision posted on its Web site Monday, the Centers for Medicare and Medicaid Services said that there was not enough evidence that use of the tests improved patients’ health.
But the agency said it would pay for the tests as part of clinical trials to gather such evidence.
The warfarin response tests, which cost $50 to $500, look at variations in two specific genes in a patient. They are among a group of new tests that seek to tailor medical treatments based on a patient’s genetic makeup. Such tests might help tell which drug would be best for a particular person, or whether a patient might be susceptible to dangerous side effects.
As many as one million or more Medicare patients a year start therapy with the drug, which is used to prevent life-threatening blood clots.
But determining the proper dose of warfarin is notoriously tricky. Even a slight change in dosage can mean the difference between too little, which would not be effective in preventing blood clots, and too much, which can cause dangerous internal bleeding. Tens of thousands of people end up in the hospital each year with complications from warfarin, which is also sold under the brand name Coumadin.
But Medicare said there was little evidence that use of the genetic test led to better outcomes for patients compared with the existing procedure, in which doctors estimate an initial dose based on a patient’s age, weight and other factors. Then they test the blood’s clotting propensity every few days and adjust the dose accordingly.
Some studies have shown that using the genetic test might allow the proper dose to be achieved more quickly. But Medicare said there was little evidence that doing so translated into a lower risk of blood clots or hemorrhages. Conclusions about health outcomes, it said, “seem to us premature, even though they are intuitively appealing.”
Medicare’s proposed decision will be open for public comment for the next month.
Edward Abrahams, executive director of the Personalized Medicine Coalition, which advocates such genetic testing, said the expensive clinical trials required by Medicare might be unreasonable for diagnostic tests.
Several diagnostic companies, including Nanosphere, Osmetech and ParagonDx, sell warfarin genetic tests to hospitals and other laboratories. Some labs offer their own tests.
The decision was “not a complete pushback,” said Bill Moffitt, Nanosphere’s chief executive, pointing to Medicare’s willingness to pay to help generate evidence of the tests’ usefulness.
Kathy Hudson, director of the Genetics and Public Policy Center at Johns Hopkins University, agreed with Medicare’s decision. “We should pay for what works,” she said.
Medical societies were divided on the issue. And the Food and Drug Administration recommends, but does not require, a genetic test for patients starting on warfarin.
Critics say that there are various practical problems with the warfarin genetic tests.
The test results often do not come back fast enough to influence the initial dose. And simply knowing which variants of the two genes a patient has does not automatically tell the doctor what dose to give. That depends on other factors as well.
Moreover, use of the genetic tests does not eliminate the need to periodically test the patient’s blood-clotting propensity. |
