You're Sure You Want to Know?

Experts advise consumers to make sure they fully understand the potential risks, benefits and limitations of any genetic screening. Many recommend avoiding home DNA tests altogether because of questions about quality control and interpretation of results. Genetic tests for more than 900 diseases are available, but the evidence for some is flimsy and regulation of the industry is scant.

For those contemplating home testing, here are some questions to consider first:

What do you hope to learn? The desire to satisfy curiosity is one thing, but learning you carry a gene for hereditary breast and ovarian cancer or cystic fibrosis can be life-changing. If the results are likely to influence your behavior -- such as whether to have your ovaries removed or to have children -- there may be a reason to proceed. But if there is virtually nothing you can do -- as in the case of genes linked to Alzheimer's disease -- you might rather not know.

Do you understand the potential results? Most people don't. A positive test rarely guarantees that a person will develop cancer or another disease, but rather that the risk of doing so is increased. Similarly, a negative test is rarely an iron-clad assurance of not getting a particular disease. Most cancers, for example, are believed to result from a complex and still poorly understood interplay between heredity and environment, not genetics alone.

Can you live for years with uncertainty or anxiety? Everyone has conditions or diseases that run in the family. Some can be postponed or even prevented with good health habits, so why not simply adopt these?

How solid is the science? Some genetic tests, such as those for hereditary breast and ovarian cancer and cystic fibrosis, are widely accepted in the medical community. Others, such as those that help one select nutritional supplements or that indicate a predisposition to depression, are not.

Why are you using a home test? If you think a home test will ensure your medical privacy, make sure you understand the testing company's privacy policy. It may offer no more protection than testing in a hospital lab or genetics center. And if you test positive, you will probably tell your doctor, and the results will then become part of your medical record.

Have you considered family reaction? A positive finding may trigger a cascade of unanticipated consequences, such as angry siblings or upset adult children who feel coerced into getting tested themselves -- or who considered testing but decided they preferred not to know.

Are you prepared for bad -- even devastating -- news? Genetic counselors agree that many people underestimate the profound psychological impact test results can have. "I really worry about people sitting there alone at home getting results and having no one to talk to," said cancer genetics specialist Scott M. Weissman.

-- Sandra G. Boodman

Sources: National Cancer Institute; National Society of Genetic Counselors; Gail H. Javitt, Genetics and Public Policy Center, Johns Hopkins University; National Institutes of Health