Genetic Test Predicts Response to Warfarin

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Stein is a leader in the new field of pharmacogenomics, which hopes to tailor medical treatment to each individual's genetic makeup. The field has been made possible by the Human Genome Project, which has mapped the full human genetic makeup. That information has led the U.S. government to sponsor programs on specific applications of pharmacogenomics and to a small but growing industry of companies developing and marketing genetic tests, such as one for warfarin sensitivity.

"The Critical Path Institute is a nonprofit organization that creates neutral ground where the FDA and industry can work together," Woosley said. "We get no funding from companies, so we can invite them to sit down with the FDA. We have brought all the companies together to develop genetic tests and asked them to share their data."

Several warfarin sensitivity tests now are available, costing perhaps $500 or $600, Woosley said.

"This is not something that changes the way doctors practice tomorrow," Stein said of the new study. "It is additional information on the relative importance of these two genes early in therapy which will refine the way that physicians use warfarin."

And the tests are useful only when warfarin treatment starts, Woosley said. They do not eliminate the need for periodic blood tests to make precise adjustments to warfarin dosage.

Nevertheless, said Dina Paltoo, the National Heart, Lung, and Blood Institute program director who oversaw the agency's funding of the study, "this can help physicians clarify what dose a patient should get, so it could reduce adverse drug effects, toxicity and bleeding."

Testing should be done because "these genetic variations are critically important in how warfarin affects each individual," Paltoo said.

More information

You can learn more about pharmacogenomics from the U.S. National Library of Medicine.