In an undercover federal sting made public Thursday, two Bay Area genetic testing companies were found to offer information that is "misleading and of little or no practical use" to consumers who purchase their tests to gain insight into their health risks.

Although Navigenics of Foster City, and 23andMe of Mountain View defended their businesses, they and two other companies were blasted by investigators from the U.S. Government Accountability Office for drawing unsupportable conclusions from the gene samples they analyzed and making health predictions that didn't always jibe with their customers' actual medical conditions.

When one investigator posing as a consumer asked whether her test data implied she was in danger of getting breast cancer, a Navigenics representative replied, "you'd be in the high risk of pretty much getting it," according to a GAO report made public at a congressional hearing Thursday.

The GAO said experts it consulted called the Navigenics' remark "horrifying" because "it erroneously implies that the tests can diagnose breast cancer and could needlessly alarm consumers."

The gene tests, which can cost consumers thousands of dollars in some cases, have come under increasing fire in recent years. Because they examine only a limited sample of a person's genetic makeup, the tests have been denounced as worthless by critics and drawn growing scrutiny from regulators.

Just last month, the Food and Drug Administration ordered Navigenics, 23andMe and three other companies to submit information verifying the validity of their tests, which the agency is considering regulating as medical devices. And two years ago, the California Department of Public Health launched an investigation into the marketing of such tests, saying some companies lacked proper state licenses.

The results of the GAO probe, which were forwarded to the FDA and Federal Trade Commission, are likely to intensify the government's oversight of the industry.

Officials at Foster City-based Navigenics issued a statement defending its business practices.

"Navigenics is approved by state regulators to operate in all 50 states, and provides its services through physicians and corporate wellness programs," the statement said.

"We are confident that we can address any specific concerns raised by the GAO report and intend to issue a more detailed response to the report as soon as possible," it continued.

In its own statement, 23andMe said "the GAO refused to discuss its flawed report with us," and added that "we are confident in our service's accuracy, reliability and value." The company also said it looks forward "to helping to develop a regulatory framework that provides standards and transparency across the industry."

23andMe's co-founder, Anne Wojcicki, is married to Sergey Brin, a co-founder of Google, which partly financed 23andMe.

The two other gene-testing companies criticized by the GAO were Pathway Genomics of San Diego, which recently announced its intention to sell its tests through Walgreens drugstores, and deCODE Genetics of Iceland. Officials with those companies could not be reached for comment.

The GAO, which had concluded from a 2006 investigation that many gene-testing companies were making unsupportable disease predictions for consumers, said it decided to do another investigation because some companies that have gotten into the business recently have been touted as being more reputable.

The GAO's report cited a number of examples where the four companies provided misleading and sometimes contradictory analyses of the DNA samples its investigators submitted.

In one case, Navigenics called a donor's risk of prostate cancer above average, while 23andMe and deCODE considered his risk average and Pathway judged it to be below average, the report said.

In another instance, a donor had a family history of heart disease, the report said, "yet all four companies predicted that she was at average risk for having a heart attack."

23andMe even provided conflicting predictions on the same sample of DNA through two different types of reports it makes available to its customers, the GAO said. In one case, for example, the donor received a report predicting she had an average risk for developing atrial fibrillation — an uneven heart beat — while another report said she had a below-average risk for the ailment.

In explaining that difference, 23andMe said its research reports provide information "that has not yet gained enough scientific consensus to be included in our clinical reports," according to the GAO report. However, the investigators faulted the company for not providing sufficient information "explaining how consumers should interpret the results."

The GAO also faulted Navigenics representatives for encouraging consumers "to make dietary changes such as adopting a Mediterranean diet or eating curry to prevent Alzheimer's disease, claims that cannot be proven, according to our experts."

Contact Steve Johnson at 408-920-5043.

FEDERAL PROBE

Among the report's findings: