The price of testing your DNA

(Money Magazine) -- Worried that your genes predispose you to developing cancer, diabetes, or some other disease? Simply curious to unlock the secrets of your DNA -- say, whether you have better-than-average odds of living to 100?

For prices ranging from $100 to $1,000 or more, that information can be yours in the privacy of your home -- at least that's the promise made by a growing number of genetic-testing companies selling their services to consumers online. Whether you can rely on what you find out is another question. Consider these factors before you buy.

Be sure the test is valid

The process is simple. You just mail in a cheek swab or spit tube, and the company tests your DNA for genetic mutations associated with a particular condition, or a host of them. But not all operators are equally reputable. Dubious signs: if the firm doesn't clearly explain the scientific evidence supporting its tests on its website or if it heavily promotes expensive diet and nutritional advice based on your test results.

Yet even legitimate outfits -- including leading players like Navigenics and 23andMe -- offer some tests whose findings are based on limited research at best. For instance, while there is hard evidence linking breast cancer and cystic fibrosis with specific mutations, the connection is not as clear for diabetes and heart disease, says Siobhan Dolan, an associate professor at Albert Einstein College of Medicine.

The surest way to know if there's a good test for your situation is to talk with your doctor or ask a genetic counselor (find one at nsgc.org). Cost of a consult: about $200.

Find out if you're covered

Many people have been reluctant to go for genetic testing, worried their boss or insurer would learn the findings. Signing up for these screens means a unique identifier of you will be sitting in some lab's database, but now you have some protection: A new federal law prohibits health insurers and employers from using that info against you.

So it's safer to ask your insurer to cover the test. But few will approve it unless you have a strong family history of the condition you want to screen for and your MD has recommended the test.

Consider the outcome

"There's not much reason to do a test unless it impacts what you can do to lower the likelihood the disease develops," says Jim Evans, a genetics professor at the University of North Carolina. For many conditions, the only effective preventive measures are to eat right and exercise -- steps you know you should be taking.

On the other hand, if you learn you're at heightened risk for, say, colon cancer, you can get evaluated with more frequency, at a younger age.

And if you find out your risk is low? That doesn't mean you won't develop the disease. Genetic research, after all, is a young science, with many disease markers yet to be found.