In an undercover investigation, government agents discovered that personalized DNA tests claiming to predict risks for certain inheritable diseases are rift with mistakes and misleading information.

"Consumers need to know that today, genetic testing for certain diseases appears to be more of an art than a science," said Government Accountability Office (GAO) investigator Gregory Kutz, in testimony before Congress on Thursday.

Genetic testing companies promise to provide an assessment of consumer’s genes using a salvia sample sent directly to their labs in plastic cups. Based on the DNA test, they provide interpretation on the results such as cancer risks and dietary guidelines to avoid diseases at high risk.

The GAO found that four genetic testing companies delivered contradictory predictions based on the same person’s DNA. Test results often contradicted patient’s actual medical histories, investigators reported.

"Sixty-eight percent of the time our donors received different predictions for the same disease," Kutz said.

The varied results is not surprising given the lack of standards of interpretation for genetic testing, an expert says. Direct-to-consumer genetics tests have been online for years without much federal regulation.

In May, when Pathway Genomics, one of the companies evaluated by the report, announced plans to market its products in retail pharmacies, the FDA intervene and said the tests must first undergo federal testing. Then the FDA issued letters to several genomic testing companies, asking them to submit their products for review.

Representatives from three genetic testing companies 23andMe, Navigenics, and Pathway Genomics defended their products on Wednesday before the House Energy and Commerce Subcommittee on Oversight and Investigations.

The companies said consumers have the right to know and access their genetic information to make informed health decisions, and they use the latest technology to deliver this.

Dr. Vance Vanier, president and CEO of Navigenics, said, "This sort of testing is safe and does not cause long term undue psychologic harm."

Rep. Bart Stupak, chairman of the subcommittee asked why the companies gave varying results.

Kutz pointed out that the investigation revealed that the results from the companies were not only contradictory, but they were supplemented by misguided information.

A home DNA test kit may not be available at drug stores any times soon but you should avoid running to get genetic testing online lured by advertising.