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Genetic Tests Offers Potent Example of Personalized Medicine
There has been much talk around National Jewish and in medical circles in general about the era of personalized medicine. A genetic test recently deployed at National Jewish illustrates how personalized medicine is already improving medical care.
Millions of people in the United States take the blood-thinning medication warfarin, also known by its trade name Coumadin. They take it for a variety of conditions, primarily to prevent blood clots that can cause heart attacks and strokes. However, an individual’s response to the medication can vary greatly; a single dose of medicine may cause dangerous thinning of the blood, which can cause internal bleeding for some people. That same dose will have no effect on others, leaving them susceptible to dangerous blood clots. The optimal dose can range all the way from 4 milligrams to 80 milligrams per week.
Doctors can use age, gender, body size, nutritional status, and interactions with other drugs to help predict the optimal dose of warfarin for a patient. However, those factors can be used to predict only some of the individual variability. And doctors can evaluate the dosing with tests done only after a patient begins the treatment.
Recently, two separate genes were identified that greatly affect the dosing of warfarin. One affects how active a given dose of the drug is, and another affects how quickly the drug is metabolized to become inactive. Individuals can carry any of several different forms of these genes. The various forms of these genes are so important that the U.S. Food and Drug Administration recently recommended getting genetic testing prior to beginning warfarin therapy.
The National Jewish Molecular Diagnostics Laboratory performs an assay to determine what form of these two genes each individual has. Results from these assays help determine the effective dose of warfarin an individual should take prior to beginning treatment, allowing physicians to safely customize warfarin treatment for millions of individual patients.
