The Downside of Genetic Testing

These days you can have your blood sampled, your cheek swabbed or your saliva analyzed to find out whether you're predisposed to Alzheimer's, various forms of cancer, lactose intolerance, restless leg syndrome -- even baldness.

Some 1,200 tests can diagnose thousands of health conditions, compared with about 100 tests a decade ago. You'll pay anywhere from $150 to thousands of dollars per procedure. Some tests are administered only by medical professionals; others are available to anyone with a credit card and access to Internet sites such as Navigenics or www.decodeme.com. To paraphrase a recent New England Journal of Medicine article: The genome is definitely out of the bottle.

These new genetic tests are intriguing, but how can you tell whether they're worth the financial (let alone emotional) expense? Could an adverse result cost you your job? Your health insurance? No one would begrudge a breakthrough that can help people understand their risk of disease, or help them prevent or manage it. But the old adage "Buyer beware" definitely applies.

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For starters, there are few guarantees that the tests are analytically valid (that is, they can be relied upon to get the right answer) or clinically valid (they actually relate to a person's health or risk of disease).

"There is no good way for consumers or physicians to be sure of the quality of genetic tests," says Gail Javitt, law and policy director of the Genetics and Public Policy Center of Johns Hopkins University. "That applies to those sold directly to consumers or administered by doctors." One way to better your odds of getting reliable results is to use only those labs that are certified under Clinical Laboratory Improvement Amendments, or CLIA, standards.

Even if you assume the tests are accurate, some have questionable utility. Few are 100% predictive, so a positive result may not mean that you'll develop a disease, nor does a negative result guarantee your immunity. Most diseases are caused by a combination of genes, lifestyle and environment that's not well understood. Nor can most tests say when a disease will strike or how severe it will be.

With any test, you should get a clear explanation, preferably from a genetic counselor, about how the data correlate with any suggested condition. That advice goes double if the tester is marketing a remedy -- say, dietary supplements.

There's also the specter of genetic discrimination, a fear that scientists say keeps patients from participating in clinical trials vital to research. Group insurance plans can't discriminate. But people who buy individual coverage aren't protected. Insurers say they don't even ask about genetic tests on applications. Still, one study found that some companies would consider denying coverage, raising premiums or cutting benefits based on genetic information.

State and federal employment and insurance laws address the issue, but they're a hodgepodge. The Genetic Information Nondiscrimination Act, a bill stalled in Congress, is intended to close the loopholes. But for now, it makes sense to approach these tests with a grain of salt -- and to share the results at your own risk.