Which genetic tests make the grade decent?

Tests for diseases with a proven link to single genes. Unlike SNPs tests, which look at gene variations that may put you at higher risk for diseases, some tests screen for specific gene mutations that have been scientifically proven to either definitively cause a disease or greatly increase your chance of developing one. Some disorders that can be screened for this way include breast cancer, colon cancer, Huntington's (a neurological disorder), and hemochromatosis (when the body stores too much iron). When people concerned about these diseases are trying to protect their privacy, some opt to use at-home versions of tests so the results won't be part of medical records. Companies that offer this type of testing include DNA Direct, Kimball Genetics, and Myriad Genetics.

Consider with caution SNPs tests from companies that use a laboratory certified by CLIA, which sets standards for US clinical laboratories. This accreditation ensures that the company uses laboratories that adhere to standards and guidelines for clinical testing. Companies using CLIA-certified labs include DNA Direct, deCODEme, and Navigenics.

Companies that offer genetic counseling. Some genetic tests deal with statistical risk that can be tough to understand and needs to be considered with your family history, so be sure a knowledgeable health professional interprets your test to avoid needless anxiety and any rash medical decisions. Some companies include free online or telephone sessions with certified genetic counselors and send detailed reports to help explain what test results really mean.

Avoid "Nutrigenomic" tests that promise to identify your risk of certain diseases and then sell you expensive vitamin regimes that are supposedly based on your genetic profile and help you prevent disease. The General Accounting Office, the investigative arm of Congress, looked at a number of these companies and found that some of these recommended supplements cost $1,200 a year and were actually similar to supplements found in stores for $35. In some cases, the vitamins exceeded recommended daily allowances, making them potentially harmful, and regardless of the different DNA sample, the "personalized"supplements sent were all the same. GAO investigators couldn't verify any of the scientific claims made by manufacturers of these tests.

Tests from companies without strict privacy policies. Despite last year's passage of the Genetic Information Nondiscrimination Act, which prohibits your insurance company and employer from using your genetic information against you, no laws yet exist to limit what genetic testing companies can and cannot do with a person's genetic information or DNA sample. Be sure that a company securely stores your DNA sample and will not sell it to be used in a research study without your permission. If the company doesn't provide this information on its Web site, ask for it directly. "Using your information without your consent is unethical," says Caroline Lieber, director of the graduate program in human genetics at Sarah Lawrence College.

Tests that don't provide documented scientific evidence validating their claims. You should be fully informed about what a test can and cannot say about your health. Companies should make scientific references available on their Web sites to document the data used for the tests. If they don't offer it, ask for it.

Even if you have one of the 18 genes linked to diabetes, it's not as if it's hardwired into your DNA that you'll get the disease on your 40th birthday--or even at all