Unraveling Your DNA's Secrets
Do-it-yourself genetic tests promise to reveal your risk of coming down with a disease. But do they really deliver?
The first big application of genetics for medical treatment, which the Food and Drug Administration is considering, will be for warfarin, a blood thinner prescribed to prevent strokes. The test identifies patients who have trouble metabolizing standard doses of the drug, which can lead to bleeding in the stomach or brain. "The genetic test is the most powerful indicator of where to start the dose," says Michael Watson, who directs the American College of Medical Genetics. "What is much less clear is whether it would reduce the number of bleeding problems." In 2004, the ACMG said that at-home genetic tests are potentially harmful. But it is reassessing that stance, says Watson, as it believes some forms, such as carrier screening, are less problematic.
To investigate the quality and usefulness of direct-to-consumer genetic tests, U.S. News tried six of them. Three were the same type of tests used by doctors for celiac disease, hemochromatosis, and breast cancer. Three othersfor Alzheimer's disease, depression, and glaucoma and macular degenerationtest genes associated with the diseases but aren't used in medical practice. Our testers were U.S. News staff members and their relatives. One staffer took a DNA sample from his 3-year-old dog, Tate, a corgi mix. We found that the value in diagnosing or predicting disease varies widely. Some could be helpful in making health decisions, while others could be worthless or even dangerous. And it's often hard to tell which is which. Our key findings:
Some tests that promise to reveal the risk of disease rely on genes that aren't up to the task. The gene tested for Alzheimer's disease, for example, indicates only increased susceptibility. And there's nothing people can do to reduce that risk.
The advice some testing firms offer patients with the results can be misleading. The test results often overstated the risk of disease or were unclear about how to interpret that risk. References to scientific research included with some of the results were outdated or irrelevant. Several tests offered generic preventive advice, such as "get regular exercise." Just two companies, DNA Direct and Denver's Kimball Genetics, offered access to certified genetic counselors trained to interpret and explain the results. Experts in the field say that interpretation is crucial because the results are usually not black and white.
Direct-to-consumer genetic tests are not regulated. The FDA does not evaluate the safety and efficacy of at-home genetic tests. Some are done in certified laboratories used by doctors and hospitals; others are not. In July, the Federal Trade Commission urged consumers to be wary of the claims of DTC genetic testing.
Although there are now more than 900 genetic tests available to doctors, most are used to screen for rare disorders like Duchenne muscular dystrophy. For decades, scientists have been hunting similar triggers for killers like heart disease and cancer. What they've found are dozens of genes that interact with one anotherand with environmental effects like smoking. For instance, women with mutations in BRCA genes have an 84 percent chance of getting cancer. But then again, there's a 16 percent chance they won't.