Consumer, beware. That's the new message from the federal General Accountability Office about home testing kits that claim to check your DNA for susceptibility to cancer, heart disease, diabetes, and other major ailments. The tests make predictions that are medically unproven and "so ambiguous that they do not provide meaningful information," the GAO report said. These "direct-to-consumer" genetic tests, which cost from less than $100 to over $1,000, have proliferated on the Internet in recent years, many promising to give consumers genetically based nutritional advice or advance warning of life-threatening illnesses.

The GAO investigators took two DNA samples via cheek swab, one from a 48-year-old GAO employee and one from the 9-month-old daughter of Gregory Kutz, the GAO's managing director of forensic audits and special investigation, and submitted the two samples under 14 phony names. The online firms reported back that the 14 fictitious customers were at risk for a wide-ranging list of serious diseases, including cancer, diabetes, and high blood pressure--despite the fact that only two people were tested.

The test purveyors defended their companies' products before the Senate Select Committee on Aging, which held a hearing on the GAO's findings last week.

"Suracell is not a laboratory and does not do genetic testing," Kristopher King, the CEO of Suracell, of Montclair, N.J., told the committee. Instead, King said, Suracell sends DNA samples from customers who buy its services to other laboratories for testing, and "provides a service to consumers" by selling them "nutritional advice and a supplement regimen that is personalized to their needs." But Suracell's website says that the "Suracell personal Genetic Health Program identifies and satisfies your individual genetic nourishment needs." The GAO said that results from the Suracell tests recommended buying expensive supplements that claimed to repair DNA; however, the experts the GAO spoke with said there is currently no pill that has been proven to fix DNA. The GAO investigators also found that nutritional supplements sold by another firm, Market America of Greensboro, N.C., as "personalized" supplements costing $1,200 a year, were common vitamins and antioxidants that could be bought in any grocery store for about $35.

"Genetic science holds great promise," said Republican Sen. Gordon Smith of Oregon, chairman of the committee, who requested the GAO investigation. "Clearly, consumers are being misled and exploited by this modern-day snake oil, and I am shocked to learn how little the federal government is doing to help consumers make informed decisions about the legitimacy of these tests."

The Federal Trade Commission is also urging consumers to be cautious about over-the-counter genetic tests, noting that companies may post your results online, which could raise privacy concerns. A new brochure offers tips and advice on these new at-home tests.

The tests under congressional scrutiny are different than the genetic tests used by doctors, which are used to look for specific genes that cause hereditary diseases such as cystic fibrosis or Huntington's disease. There is clearly a genetic component in heart disease, cancer, and diabetes, but scientists think many different genes are involved in each, and as yet there are no tests to readily identify who will be affected.

"This is just so loosey-goosey," Smith told the test purveyors. "I'm really concerned about what you're selling."