How reliable is personal DNA testing?

In an e-mail, 23andMe spokeswoman Jane Rubinstein adds that the company has met with the Food and Drug Administration and "anticipates actively working with the FDA," including sharing a proposal on ways to regulate the genetic-testing industry. "Because we are in early discussions we do not want to be more specific," Ms. Rubinstein says.

Geneticist Davies, author of the new book "The $1,000 Genome," found that receiving his gene-test results was an "empowering and exhilarating" experience, even though he knew the results should be viewed as very "preliminary." "It's the very early days," he says. "For the most part, the DTC companies do a good job of stressing that, [but] I think they can do a better job."

He's also critical of the GAO report. "It seemed to me they had an answer in mind and then went about proving their thesis," Davies says. "I just didn't like the way it was done at all."

In the view of Hank Greely, director of the Center for Law and the Biosciences at Stanford University, genetic testing is overdue for stronger federal regulation, including a ban on DTC tests done without the supervision of a doctor or other health-care provider.

"If [a test] is health-related, it should go through a health professional ... who can help and advise you as to what it means," he says.

All the leading DTC genetic-testing companies say they offer either in-house counseling or referrals to genetic counselors to help explain the results. But interpreting the data can be tricky business.

Based on identical test results, for example, a customer may be told that she has a five-times-higher-than-average likelihood of contracting a certain disease. Or the same data could be rephrased to say that her chance of contracting that illness are 5 in 1,000 instead of the average of 1 in 1,000, a much less troubling message.

What's more, there's wide agreement that genetic factors play only a partial, and poorly understood, role in the development of disease. Other variables, such as a person's lifestyle and environment, are also part of the equation and make extracting the role of genes more complex.

"The companies are pretending that the science has advanced enough that they can say something. But it hasn't," Dr. Greely says.

The problem of how to properly conduct genetic testing and inform participants arose again in August when the University of California, Berkeley, asked more than 5,000 incoming freshmen and transfer students to submit saliva samples for genetic testing as part of an effort to teach them something about genetic tests. The students were to be tested for three supposedly benign traits: their responses to dairy products, folic acid, and alcohol. The program was halted after serious concerns were raised about it. Those students who did submit samples now will not receive their results.

"You're going to tell 17- and 18-year-olds that they are efficient metabolizers of alcohol? What are they going to do with that information?" CGS's Ms. Darnovsky asks. "That seemed to me to be so irresponsible."

Current genetic tests analyze about 600,000 SNPs (single nucleotide polymorphisms) or 0.1 percent of the entire genome. What these DTC genetic-testing companies are doing is "a dying technology," Greely says. Whole-genome sequencing is a far more elaborate, and potentially much more helpful, look at a person's genetic makeup, he says. The cost was $50,000 last year and is down to $10,000 this year. In two or three years it will be $1,000. "That will be the next direct-to-consumer issue," he says.

"Everybody's whole-genome sequence will say something scary, either for them directly or for children they may have in the future or may have had in the past," he says. "The idea that people are just going to get this [information] over the Internet [without counseling] scares me."

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