Its hard to get straightforward health guidance from personal genome tests, which are banned in some places. But one way to make them more meaningful is to let more people buy them.

It was easy to send my spit to 23andMe, a personal genetics company based in Mountain View, California. I filled the tube that came by mail with a few milliliters of saliva, mixed in the preservative solution, and screwed on the cap, and my sample was ready to be mailed. Soon I would know my risks for Alzheimers, breast cancer, and obesity, and Id have an idea what medications I should avoid.

Well, not exactly. As in most of human genetics, whats tricky about consumer-friendly tests is interpreting the significance of DNA variation. A couple of weeks after shipping off my tube, I got an e-mail notice that my results were on 23andMes website. While it was fun to click through my ancestry reports, I was less compelled by the analysis of the genetic traits that could influence my health.

The biggest disease risk in my report? I have a 5.2 percent chance of developing restless leg syndrome later in life24 percent greater than the average person, who has a 4.2 percent risk. My risk for Alzheimers is slightly lower than average and my risk for obesity is typical. But these conclusions are not particularly meaningful. New studies could uncover variants in my genome that carry a significant risk for dementia later in life. And for obesity, genetics can be overshadowed by lifestyle.

The results did contain some useful information, however. For example, my genome carries signs that I have an above-average sensitivity to a common blood thinner. Currently, I dont need such a drug, but if that changessay, if I suffer a heart attackthen this knowledge could be critical in helping a physician determine the proper dose of a potentially life-saving medication. I also found motivation to switch to decaffeinated coffeemy report says I am a slow caffeine metabolizer, which is associated with a risk of heart attacks for multi-cup-a-day users like me.

23andMe Personal Genome Service

In some ways, I was lucky that I found nothing monumental in my report. About 40 to 50 percent of customers end up with results like yoursthey dont have anything that jumps out very strongly, says Joanna Mountain, senior director of research at 23andMe. But for many, the results are potentially more significant. For example, for macular degeneration, the risks [that are indicated in the reports] range from 0.1 percent up to 74 percent, Mountain says. For heart disease, theres a big range10 to 50 percent.

It can be difficult for most people to understand what these ranges mean, though. And for now, its not clear how receptive the medical community is to helping. Ive had patients bring me these reports, and I dont spend a lot of time reviewing the results because this is not a test I would have ordered, says Sharon Plon, a geneticist and physician-scientist at Baylor College of Medicine in Houston. Whats missing is proof that these tests can inform and improve patient care, she says: Physicians are going to shy away from using them unless they become part of evidence-based medicine.

Typically, personal genetics companies like 23andMe determine which particular DNA base pairs each customer has at places in the human genome that are known to vary from person to person. The companies then interpret the results of scientific studies to tell customers what their results mean. The tests are sold directly to consumers for as little as a few hundred dollars, without the involvement of a health-care provider. In 2010, the FDA sent letters to several companies warning them that their products were considered medical devices subject to regulation, although exactly how the oversight would happen still hasnt been firmly established. That same year, the Government Accountability Office sent samples to four companies and got conflicting results.

Because interpreting the results is so uncertain and the relationship between genetics and disease risk is sometimes weak in the first place, some critics oppose selling these tests directly to consumers. Such sales are restricted in some countries, such as France, and in a few U.S. states, including New York and Maryland. The American College of Medical Genetics and Genomics stance is that the tests should be taken with guidance from an expert who can assess the validity of the results and explain the actions that could be taken in response, says executive director Michael Watson. New studies on the connection between DNA and disease or drug response are published every week. Some of these studies establish a previously unknown link; others may add more weight to a known association; yet others may contradict or disprove what was once thought to be meaningful. The results of many of these tests are very complex, says Plon.

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Why We Have a Right to Consumer Genetics

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