Consumers who buy genetic tests in hopes of seeing what diseases they are likely to contract may be misled, according to a report from the U.S. Government Accountability Office. In addition, the results can vary so widely that they are “of little or no practical use,” the report concludes.

Congress and the U.S. Food and Drug Administration are trying to regulate this nascent but burgeoning field even amid uncertainty over the meaning of test results that indicate someone has genetic risks for certain diseases. “The problem with these marketing practices is that it is not clear today whether the exciting scientific developments in human genetics research actually transfer into ways to improve and individualize health care,” Rep. Henry Waxman (D-CA) said Thursday at a congressional hearing on the industry.

The most shocking findings from the GAO report come from a series of undercover phone calls made to 15 genetic testing companies. Fictitious consumers asked about test reliability, privacy policies, and sales of nutritional supplements or other products tailored to an individual’s DNA. In the phone calls, people who sound like telemarketers are heard giving unsubstantiated and sometimes nonsensical medical advice. For example, at least four companies “claimed that a consumer’s DNA could be used to create personalized supplements to cure disease,” according to the GAO. Two companies condoned the “potentially illegal practice of testing DNA without prior consent.” Overall, the GAO found, 10 of the 15 companies engaged in fraudulent or deceptive marketing.

Both congressional leaders and company representatives said they were dismayed after hearing the calls. However, lawmakers and the companies maintained that genetic testing has a strong potential future in medicine, and that it would be unfortunate if snake-oil salesmen stained the entire industry.

This new level of federal scrutiny follows three years of minimal regulation for direct-to-consumer genetic testing. Several testing companies sprung up around three or four years ago to take advantage of rapidly expanding knowledge of how human genetics can be linked to diseases such as diabetes and cancer. The tests, which can be ordered over the Internet and range from about $100 to $1,000, typically analyze a person’s genome for common genetic variations that have been linked to a relatively minor increased risk for a particular disease.

The industry has been under fire since its inception, as physicians and scientists question whether this information about modest risks can truly be used to make health-care decisions. Complicating matters further are claims from many of these companies that they are not providing a medical service and therefore do not require regulation from the FDA, even though many of their marketing materials allude to the promise of better health.

To evaluate direct-to-consumer genetic testing, the GAO sent DNA samples from five donors to four companies–23andMe, Navigenics, Pathway Genomics, and DeCode–for testing. These four are “touted as the most reputable in the industry,” said Gregory Kutz, managing director of Forensic Audits and Special Investigations at the GAO. For each of the donors, one sample used factual information, while the second had fake age and ethnicity information. GAO investigators then made undercover calls to the companies to discuss the results.

All five donors received conflicting results, said Kutz. For example, having submitted his own DNA as a sample, Kutz learned that he was simultaneously at less than average risk, average, and above-average risk of developing prostate cancer, depending on the company that did the test. “I believe these results show the tests are not ready for prime time,” he said.

That should be of little surprise to those closely following the field. Craig Venter, who led the private arm of the human genome project, published a commentary with similar findings in the journal Nature last year. Francis Collins, head of the National Institutes of Health, wrote about a similar discovery when he tested different services for his newest book, The Language of Life.

The discrepancy comes from the fact that the different companies calculate risk using different algorithms, which vary in their criteria for which genetic variants to include. During the hearing, Ashley Gould, general counsel for 23andMe, agreed that the field needs standards for calculating risks. The company has already reached out to the FDA and the NIH for help in developing such standards.

Both Jeff Shuren, director of the Center for Devices and Radiological Health at the FDA, and James Evans, professor of genetics and medicine at the University of North Carolina, said they believed that most tests’ analytic results–their ability to correctly detect a specific variation– were accurate. But calculating and assessing clinical validity–using the information to accurately predict disease risk–is an entirely new science. “No one knows how to interpret this data,” said Evans. The FDA has begun discussing regulation of a broader category of laboratory tests, and how to define and regulate clinical validity is a major issue.

The GAO report also found problems with how the companies dealt with consumers of African or Asian descent. Because most genetic research has been done on Caucasians, it’s unclear how well the findings translate to people of different ethnicities. While the companies do point this out on their websites and in their reports, they didn’t prominently disclose this when consumers were ordering and paying for the tests, Kutz said.

Some companies named in the report and the congressional hearing complained that they were being lumped with unnamed companies that came off as outright charlatans, such as the ones selling supplements purportedly tailored to an individual’s DNA. However, the more well-known companies didn’t necessarily shine in comparison. In the audiotapes, a representative from Pathway told a caller it was okay to surreptitiously collect her fiancé’s DNA and have it tested as a gift. That would be illegal in 33 states. When one caller asked whether being classified as having a high risk for developing breast cancer meant she would definitely get the disease, a representative from Navigenics responded, “you’d be in the high risk of, you know, pretty much getting it.”