Besides the genetic profiling companies, the health-related direct-to-consumer testing options available today can be lumped into four general categories:

 

·        On the periphery: This group capitalizes on wellness and complementary medicine trends. Nutrigenetic tests, for instance, offer to pinpoint your nutritional needs by checking for gene variants associated with metabolism, nutrient absorption, and antioxidant defense. Last year, the Government Accountability Office (GAO) checked out these claims by creating 14 fictitious customers and sending in DNA from a 9-month-old baby girl and an unrelated 48-year-old man to four web sites. The results that came back seemed tied more closely to lifestyle factors that investigators had made up for the fake test-takers than to the genetic material in the real samples. The GAO concluded that these companies “mislead consumers by making predictions that are medically unproven and so ambiguous that they do not provide meaningful information to consumers.” While the results stirred calls for more regulations, so far nothing has changed.

 

·        Complex and hard to predict: Another set of tests searches for DNA variants associated with a risk for variable and complex disorders such as Type-2 diabetes. Geneticists are vigorously debating the value of gene tests for these conditions as they may be no more useful than simply heeding a doctor’s advice. The diabetes test offered by San Francisco-based DNADirect, for instance, looks for a variant in TCF7L2. In one recent analysis, researchers combined TCF7L2 with two other common variants associated with diabetes susceptibility and found that their collective predictive power was very small—a disease risk of about 10 percent with all three alleles present—but might still be useful. A negative result doesn’t mean the patient can cross the disease off his or her list of concerns; a positive offers a hint but not a prediction. If you find that you have a slightly higher risk for diabetes, asks Kaiser Permanente geneticist David Witt, “What can you do about it that you couldn’t do anyway?”

 

·        Dosage advice: A number of tests check for gene variants associated with metabolizing drugs such as warfarin, tamoxofin, and Valium. New labels on the widely prescribed blood-thinner warfarin, for instance, warn that people with variations of CYP2C9 and VKORC1 might need lower doses. Somewhere between 5 to 10 percent of people have versions that may put them at risk for life-threatening bleeding. Even with information about higher drug sensitivity, though, admonishes the FDA, doctors will still need to do regular blood tests to check proper clotting. And they must take into account age, diet, and other medications. These tests’ significance when writing prescriptions is still unclear, and no clinical trials have yet demonstrated that they offer any better protection than an alert physician.

 

·        Powerful test, small population: Some of the first genetic tests that became broadly available to consumers through doctors’ offices also quickly went online. Salt Lake City-based Myriad Genetics sells a screen for mutations in BRCA1 and BRCA2, which are thought to underlie between 5 to 10 percent of breast and ovarian cancers. Five years ago, Myriad became the first company to promote a genetic test directly to the general population through a radio, print, and television advertising campaign. In recent months it began television ads in the Northeast that suggest that a single relative with breast cancer might be reason enough to get the test. Myriad requires a doctor to be involved in ordering online. DNADirect.com, however, legally offers the same test in 25 states and Washington, D.C., without any practitioner okay. While this screen clearly has predictive power, only about 1 in 400 women are likely to have the mutation.

 

The at-home tests differ from carrier testing or prenatal screening for single gene disorders such as Tay Sachs or sickle cell anemia, which do offer clear predictive value—but aren’t generally offered online. Those tests also engendered debate about potential discrimination, proper counseling and, in cases such as Huntington’s Disease, the practical usefulness of genetic knowledge.