Lots of ads on TV these days for various DNA test kits. You send a sample off to the company and they tell you . . . what? What are they actually telling you? Is this real scientific exploration or just intrusive data mining? —Jenny

If you're suggesting the as-seen-on-TV approach might not be the best way to understand the most complex, private and fundamental parts of your personal makeup, Jenny, you might be onto something. In hospitals and laboratories, the field of genetic testing is still something like the Wild West. In your bathroom, it's practically the OK Corral. The nut of the issue is that these at-home tests are increasingly looked at as avenues for determining folks' personal dispositions toward certain illnesses or conditions—say, breast cancer. The objections are what you might imagine: You really want to learn something like that through the mail? Or make medical decisions based on it?

Let's start with the wide-angle view. DNA testing—typically looking at cells collected via cheek swab or blood or saliva sample—can tell you any number of things. The U.S. National Library of Medicine lists seven categories, ranging from newborn screening (all states require testing for phenylketonuria, a genetic condition that can lead to intellectual disability if left untreated) to forensic analysis (establishing paternity) to carrier testing—like identifying mutations of BRCA1, a gene that ordinarily produces tumor-suppressing proteins in the breasts.

Even in the hands of professionals, genetic tests aren't surefire. A 2016 paper in Reproductive Biology and Endocrinology suggested that standard screening of in-vitro embryos before implantation might be needlessly hurting the patients' chances of becoming parents: A higher-than-expected number of false positives for aneuploidy (abnormal chromosome count) likely means healthy embryos are getting discarded.

Maybe more worrisome, a 2016 Boston Globe investigation described would-be parents spending thousands of dollars on multiple rounds of prenatal genetic tests at for-profit labs, sent there by genetic counselors who might have undisclosed financial ties to the companies doing the testing. One pregnant client said a counselor told her that her daughter had a "near certainty" of being born with Turner syndrome, a growth disorder, claiming the test had a false-positive rate of just 1 percent and recommending the lab run a second test. Instead the woman consulted a second counselor, at Tufts Medical Center, who figured the child's chance of having Turner's was only 14 percent. Another Globe story, from 2014, reported that companies doing prenatal risk screening weren't always being clear about the tests' limited reliability; some patients had gotten screening results back and chosen abortion, but subsequent exams on the fetuses showed they'd been fine.

And again, all this is with trained pros administering the tests and interpreting the results. It's hard to figure accuracy improves when the amateurs give it a shot instead.

Of course, testing for health risks is just one kind of DNA analysis, and others concern themselves with more benign matters, like genealogy. Some companies offer genetic tests they say can help you optimize your beauty and exercise regimens. But overall this market is skyrocketing—estimated to hit $340 million worldwide by 2022, up from $70 million in 2015, according to The Guardian—and health and disease screening are clearly where it's headed. Earlier this year the Food and Drug Administration approved the first direct-to-consumer test (as they're called) to help customers determine their risk of developing diseases including Parkinson's and Alzheimer's.

Otherwise, though, the FDA has struggled to assert regulatory control over these at-home tests; the vast majority on the market, indeed, aren't FDA-regulated. Historically, the agency has worried consumers would use them to make medical decisions, and they're not the only ones. In a 2015 statement, the American College of Medical Genetics and Genomics called for a set of minimum standards to apply to direct-to-consumer genetic testing, stressing the needs for clear explanation of what such tests can and can't tell people about their health, counselors to explain the results, and privacy safeguards.

Which brings us to the last part of your question: What becomes of the data generated by genetic testing? It's true the testing service may reserve the right to sell it—make sure you read the fine print before spitting into any test tubes. But I'd suggest the risk is actually less in how the test companies might use your results than in how you do.

Here's a scenario: Since 2008, health insurers have been forbidden from engaging in "genetic discrimination," like denying coverage based on (to return to our earlier example) a BRCA1 mutation. But that's not true for life, disability or long-term-care insurance. And, of course, when you apply for something like life insurance, you're expected to self-report your medical information.

So say you've taken a genetic test—even just a fun one. Finally, you can confirm that Viking ancestry—that happens as a byproduct to identify a genetic predisposition toward some disorder. That's information you're now obligated to share, unless you'd like to lose that policy down the road—or lose the payout due to your beneficiaries after your death—if your insurer finds out. For now, maybe just stick with the Slanket.

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