In the decade since scientists drew their first map of the human genome, medicine has used it to make immense progress. But the map has often proven hard to follow.

In 2000, President Clinton announced that scientists had finished the first map of humans' genetic makeup. Hopes ran high that science would soon use that map to find new ways of preventing, diagnosing, treating, and curing diseases.

A simple blood test or swab inside your cheek would unlock the secrets in your unique set of 20,000-plus genes. Passed down to you by your parents, these genes control far more than your height or eye color. They also influence your risk for diseases.

Since then, we've made great progress, but genetic medicine--and the best ways for consumers to make use of it--have proven tough mysteries to crack.

The Progress ...
In the past decade, experts have developed genetic tests for more than 2,000 diseases. Some tests look at a single gene to find rare disorders or inherited genetic mutations. Others look at a series of genes that raise or lower your risk for common diseases, such as cancer or diabetes.

Moving toward "personalized medicine," some tests (with more on the way) can say which drugs you should or shouldn't take, and in what doses. Some tests even claim to tell you which foods you should eat, which supplements you should take, and which sports could make your child a star.

A series of articles in the New England Journal of Medicine (NEJM) reviewed the progress. The Food and Drug Administration (FDA) now requires warnings on drug labels when certain genetic markers have been tied to side effects--for example, for two blood thinners given to heart patients. Drugs have been designed to fight specific mutated cancer genes. For some cancer patients, genetic tests help decide who's at risk for a relapse, who would get the most help from certain drugs, and who isn't likely to benefit from chemotherapy.

Genetic testing can help warn of rare breast, ovarian, and colon cancers that run in families, according to the National Institutes of Health. And genetic tests can uncover cystic fibrosis, sickle cell anemia, and Down syndrome in an unborn child.

... And the Challenges
Despite such advances, the promise of genetic testing has yet to be fully realized. For example, the possibility that a DNA test can tell you if your athletic child is the next LeBron James is "complete garbage," according to an expert cited by the U.S. Government Accountability Office (GAO).

A 2010 study led by Brigham and Women's Hospital researchers in Boston offers a glimpse of the problems researchers can run into as they seek to apply genetic data to patients' treatments. Their study found that growing genetic knowledge hadn't made it easier to pinpoint the risk for heart trouble.

The study looked at 101 genetic variants that have been tied to heart disease. Those variants were useless when it came to predicting which of the 19,000-plus women the study tracked for a dozen years would get heart disease. The traditional method of asking patients if they had any family history of heart disease was much more effective.

Part of the problem, notes the Centers for Disease Control and Prevention, is that researchers have identified just a tiny slice of the genetic element of most diseases. What's more, genes aren't the only factor. Your family background, medical history, environment, lifestyle, and diet also determine whether you'll get a particular disease.

Buyer Beware
If you're considering direct-toconsumer (DTC) genetic tests, be wary. No federal rules govern their accuracy and reliability. The FDA is mulling whether to regulate them.

Two GAO undercover investigations of DTC companies have found problems. Recently, the GAO bought 10 tests from four companies for $299 to $999 per test. The GAO sent each firm two DNA samples from each of five donors. One sample had truthful information about the donor; the other had fictitious information, such as the wrong age or race. After receiving the test results, the GAO placed undercover calls to the testing firms seeking health advice.

The GAO's conclusion: "Misleading test results are further complicated by deceptive marketing and other questionable practices." The GAO found:

• Contradictory results: Using the same 48-year-old man's DNA samples, the four companies concluded that his risks for prostate cancer and high blood pressure were variously below average, average, or above average
• Predictions at odds with donors' actual medical conditions
• Failure to provide promised expert follow-up advice
• Failure to reveal they could not provide complete results for African-American and Asian donors
• False claims that your DNA can be used to create personalized supplements that can fix DNA damage or cure disease
• Fraudulent endorsements from high-profile athletes

"Perhaps most disturbing," the GAO says, "one company told a donor that an above-average risk prediction for breast cancer meant she was 'in high risk of pretty much getting' the disease." GAO experts found that statement "horrifying" because it implied the test had all but diagnosed cancer.

'No Value'?
In the NEJM, a federal researcher reviewed tests that claim to gauge your risk for scores of diseases. He advised doctors to tell patients that "at present the results of such testing have no value in predicting risk" or indicating how your doctors should treat you.

Are you still interested in genetic testing? At a minimum, the American College of Medical Genetics suggests you enlist the help of a knowledgeable professional. A certified medical geneticist, for instance, can help you decide whether you should get such tests and, if you do, help you make sense of the results.

Genetic Testing FAQs

Q. Why do people have genetic tests?
A. Some have signs of a disease, and others suspect they have an increased risk for one. Still others worry about passing a disease to their children. Talk with your family doctor if you think you or your offspring have a high risk for an inherited disease. He or she will ask you about your health and the health of your blood relatives to determine your risk.

Q. What can I gain by being tested?
A. You may not worry so much about getting a disease. If the test finds you do have an increased risk, you may be able to reduce that risk by altering your lifestyle or taking medication. And your doctor will know how often to check you to see if a disease is developing.

Q. What's the downside of testing?
A. After testing, you may worry about getting sick. Testing can worsen stress, guilt, or family relationships. There's also the cost, which can range from a few hundred dollars to more than $1,000 for at-home testing. Your health insurance may not cover that cost. And in some cases, there may be no way to prevent or treat the illness even if testing finds you're at risk.

Q. Can testing cause problems with employers or insurers?
A. Federal and some state laws prevent insurers from denying coverage or raising premiums based on genetic tests. Federal law also bars the U.S. government or employers with more than 15 workers from discriminating against employees or job applicants based on such tests. Still, if you're considering a genetic test, ask what safeguards protect the privacy of results.

SOURCES : American Academy of Family Physicians, National Institutes of Health

By Bruce E. Beans, a feature writer for Vitality. For more information, visit the National Library of Medicine at www.nlm.nih.gov/medlineplus and search for "genetic testing."

© Krames StayWell. Information is the opinion of the sourced authors and organizations. Personal decisions regarding health, diet, and exercise should be made only after consultation with the reader's own medical advisers. This material may not be reproduced for redistribution without written permission from Krames StayWell.