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How reliable is personal DNA testing?

DNA testing deliver uncertainty. Faulty interpretation and incomplete genetic research are cited in direct-to-consumer tests.

By / Staff writer / September 15, 2010

Highly magnified strands of human DNA. Testing, especially direct-to-consumer kits, offer uncertain information.



Kevin Davies sent a sample of his saliva to a genetic testing laboratory in Iceland to learn about his health risks. When he received his results, Mr. Davies learned that, based on his genetic makeup, he had an above-average risk of contracting prostate cancer.

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Out of curiosity, he checked back three months later and found that the company, called deCODE, had changed its assessment: His risk was now below average.

DeCODE had recalculated its algorithm, based on new data. Davies, who is himself a geneticist by training, wasn't too surprised by this about-face: "The information that these companies can give you can change and evolve over time," he says.

That isn't the only way today's genetic tests offer slippery conclusions. According to a US government study, results often vary widely among genetic-testing companies, largely because each has its own way of choosing and analyzing data.

When the project to map human DNA was finally completed in 2003, many predicted a revolution. Drugs could be chosen to match individual patients with maximum therapeutic effect and minimum side effects, the advent of so-called personalized medicine.

But a summer spate of troubling stumbles for genetic-testing companies and programs shows just how long and twisting the road can be between advances in basic scientific research and their application.

It also has spotlighted the question of how medicine will be practiced in an era when anyone can research ailments and treatments on the Internet, sometimes becoming more familiar with new therapies and tests than their physicians.

In July, a report from the US Government Accountability Office presented at a congressional hearing on genetic testing roiled the waters. The GAO found that direct-to-consumer (DTC) genetic test results were "misleading and of little or no practical use to consumers." As a test, the GAO sent identical saliva samples to four leading companies. It found that disease predictions varied widely, "indicating that identical DNA can yield contradictory results" from each company.

The GAO also found 10 "egregious examples of deceptive marketing" by companies, such as saying they could predict what sports children would be good at. Two companies said it would be fine for a woman to surprise her fiancé with the results of his genetic test, which she would secretly have done on him, an obvious privacy violation.

The problem is "there's no gold standard. There's no way of saying what would be the correct answer" in interpreting the data that companies present to their customers, says Troy Duster, a sociologist at the University of California and New York University who has long studied the ethical issues surrounding genetic research.

"The idea that consumers should be relying on this kind of spurious information whose interpretation is so questionable, and whose utility is so questionable – it's bogus," says Marcy Darnovsky, associate executive director of The Center for Genetics and Society (CGS), a nonprofit group in Berkeley, Calif.

In August, an article in the prestigious New England Journal of Medicine urged that consumers be protected from "unrealistic claims and misinterpretations of complex, dynamic genomic information." In many cases, the authors said, "there is little or no evidence of the clinical validity of genetic tests."

Genetic-testing companies beg to differ.

"We are confident in our service's accuracy and reliability," says a blog entry on the website of 23andMe, a genetic-testing company based in Mountain View, Calif., one of several that were singled out for criticism by the GAO. "It is widely accepted that the technology we are using is sound." The company called the GAO report "deeply flawed" and "unscientific" and noted that the "GAO did not find any problem with the underlying data that we provide...."