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Monday, December 30, 2013

Is Looking into the Genetic Crystal Ball Worth It?

Last month the FDA ordered 23andMe to stop selling their genetic testing kit, saying that the company had not proved the effectiveness of their tests.

Before that order went into effect, Kara Peikoff, decided to check out how reliable these tests were. She had her DNA tested by three different companies, and reported on the results in The New York Times. It turns out these tests are basically worthless. They provided contradictory results for some diseases they tested for, and textual interpretations of the results differed markedly: one company said her risk for type 2 diabetes was "medium" at 10.3%, while another company company said it was "decreased" at 15.7%.

These tests claim they check for hundreds of diseases, but:
There are only 23 diseases that start in adulthood, can be treated, and for which highly predictive tests exist. All are rare, with hereditary breast cancer the most common. “A small percentage of people who get tested will get useful information,” Dr. Klitzman said. “But for most people, the results are not clinically useful, and they may be misleading or confusing.”
That makes these tests worse than worthless, and actually harmful. Which means they're just ripping their customers off.

What makes more sense, if you're worried about a genetic predisposition to a particular disease that runs in your family, is to get tested for that disease. That's what Angelina Jolie did: she decided to have a preventive mastectomy after genetic testing showed she was likely to develop breast cancer.

And if there's a disease that you may get that has no effective cure or for which there are no preventive measures (such as Parkinson's), you may not wish to be tested at all. It really depends on what kind of personality you have. If you would feel less stressed by knowing what your chances are, even if you knew it was likely, you should consider testing. But if you'd feel that the angel of death was standing over you for the rest of your life, you may well be happier not knowing.

At this point, these tests are woefully inaccurate because they examine only an extremely small number of SNPs (segments of DNA). Until the cost of whole-genome sequencing drops to an affordable level, these tests are a total waste of money.

As one of the doctors for The Times article said:
[The tests] may be interesting as a kind of entertainment, but do not take them seriously yet in driving your health care or your lifestyle. If you want to spend money wisely to protect your health and you have a few hundred dollars, buy a scale, stand on it, and act accordingly.

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