If you’re curious about whether your genes put you at elevated risk for cancer, hypertension, Alzheimer’s, heart disease, diabetes or a wide range of rarer “inheritable diseases,” you may be tempted by ads for the many at-home (also called direct-to-consumer) genetic tests.
Costing several hundred to a thousand dollars or so, they’re now sold on the Internet, and there are plans to sell them in drugstores. Some tests claim to provide personal nutrition advice based on your genetic profile. Usually all you have to do is rub a swab inside your cheek and mail it to the company, which will scan your DNA, looking for mutations and variations that suggest increased risk, and then send you the results.
Sounds clear-cut, but genetic testing—especially when done at home—raises many practical and ethical questions and problems.
Too much information? Or too little?
Home genetic tests fall into a regulatory gray area. They have not been reviewed by the Food and Drug Administration (FDA) or any other agency, unlike most physician-ordered genetic tests or other kinds of at-home medical tests. There’s little or no evidence that the great majority of the tests are accurate, reliable or “clinically meaningful” (in other words, useful or practical).
In recent years, the FDA has told some companies that the tests are medical devices—that is, they are intended to diagnose, prevent or treat diseases—and thus the companies should submit data and get FDA clearance in order to continue marketing them. The companies, meanwhile, say that they’re just supplying information rather than diagnosing or treating diseases, and that people have a right to know what’s going on in their DNA. So far, the FDA has not barred the sale of the tests.
One problem is the overblown claims made in much of the marketing material. In most cases, there’s no research showing that the results of the tests can help people prevent disease or lead to better treatment or longer lives. Let’s say a healthy young man takes a genetic test at home and finds out he’s at high risk for eventually developing prostate cancer. What should he do? Get frequent PSA tests, a biopsy, ultrasound? It’s not certain that any step would add even a day to his life.
And that’s assuming the test results are accurate to begin with—which is questionable. In 2010, the Government Accountability Office (GAO) published results from its investigation of home genetic tests, showing that companies produced inconsistent or even contradictory results from the same DNA sample. The GAO also cited many examples of deceptive marketing, bogus claims and erroneous advice, including companies using the results to sell “customized” supplements that supposedly help cure disease or repair DNA damage.
Lots of unknowns
Before doing any genetic testing, discuss the risks and benefits thoroughly with your doctor or a genetic counselor. You may well decide not to be tested. Who will know the results of the test? What will your options be? Will your health insurance be affected? How accurate is the test?
Moreover, the results of genetic testing are often ambiguous. Relatively few diseases are controlled by a single abnormal dominant gene (such as Huntington’s disease) or a pair of abnormal recessive genes (such as Tay-Sachs disease or sickle cell anemia). Most are multifactorial—influenced by several genes, the passage of time and the social and physical environment. That is, a gene or genes that may put you at risk for, say, type 2 diabetes, might not come into play if you maintain a healthy weight, eat sensibly and exercise as you age.
With those more complex diseases, testing may saddle you with unanswerable questions. If an abnormal gene or mutation turns up, you may feel doomed and see yourself as a sick person—even though it doesn’t guarantee you’ll get the disease, or tell you when you’ll get it (at 50? or 90?). On the other hand, a good test result is no guarantee you won’t get the disease, especially since most tests look only at a small portion of the more than 20,000 genes in the body.
Bottom line: The science of genetic risk prediction holds great promise, but is still in its infancy. For now, be wary about genetic testing, especially do-it-at-home tests—unless you have a special family history, have consulted with a qualified professional and have thought long and hard about the pros and cons.
When testing may be warranted
In some circumstances, it’s reasonable to consider genetic testing, when it’s done in conjunction with a health-care professional knowledgeable in genetic medicine and by a specialized lab. For instance:
Breast cancer: About 2 percent of women have a family history strong enough to warrant testing, according to the U.S. Preventive Services Task Force. If the results are positive, you should have frequent mammograms and other testing (such as MRI), and may even decide to have prophylactic surgery.
Colon cancer: If you have a strong family history of this cancer, you need frequent colonoscopies to find and remove polyps. Genetic testing can be helpful in determining if you need even more frequent colonoscopies.
Dementia: Three rare gene mutations are known to almost always produce early onset of Alzheimer’s disease, but account for less than 1 percent of all cases. Another gene is linked to increased risk for the more common late-onset Alzheimer’s, though most people who have this gene do not develop the disease. Testing remains controversial, since if you have one of the genes, what can you do? So far there is no way to prevent Alzheimer’s.
Pregnancy: If you are planning a pregnancy and certain disorders run in your family and/or you belong to an ethnic or racial group that tends to have certain disorders (such as Ashkenazi Jews, who are at risk for Tay-Sachs disease, and African Americans, at risk for sickle cell anemia), you should discuss genetic testing with your doctor.
Published February 01, 2012