Decoding Your DNA: What to Consider Before Genetic Testing

 Katherine Hobson
  9th-Sep-2018

NOT LONG AGO, GENETIC testing was an expensive endeavor done strictly through the health care system. Nowadays, you can mail a saliva sample directly to companies, pay a few hundred dollars and get details on factors that may affect your disease risk. According to proponents, arming people with their genetic information helps them take charge of their health. But for most conditions, it's unclear whether learning about predisposition motivates behavior change. So before you spit in a test tube and put it in the mail, consider:

Why you want the test. Following a 2013 crackdown, the Food and Drug Administration has begun approving tests that offer genetic information to people without a physician's involvement, and has recently taken action to streamline the path to market. Through 23andMe, you can get screened for mutations you might pass on to your kids and for genetic variants linked to such conditions as age-related macular degeneration, Parkinson's disease, late-onset Alzheimer's disease and some hereditary breast and ovarian cancers. Meantime, Veritas, Color Genomics and some companies that sell their products through the online consumer genomics marketplace Helix require a doctor – in some cases your own, other times one that's assigned to you – to sign off on ordering tests that gauge your genetic risk of certain hereditary cancers, heart conditions and immune disorders, for example.

If health-risk information is what you're after, learn the limitations of the test you're considering, says Cecelia Bellcross, director of the genetic counseling training program at Emory University School of Medicine. Some harmful gene variants are highly predictive of future health, as with mutations in BRCA1 and BRCA2 genes for breast and ovarian cancer, and there are concrete ways to manage that risk. Others aren't nearly as prognostic. Think hard about how you'd feel if the results were negative, positive or uncertain, what action you might take afterward and how the results might affect your family members – who may get clues about their own genetic makeup from your results. Some companies include genetic counseling as part of their packages; if you need more input on the potential risks and benefits, talk to your doctor.

You won't get the full picture. Companies analyze your DNA to varying degrees, and the cost differs accordingly: Veritas, for example, charges $999 for whole-genome sequencing, the most extensive sequencing strategy. Color Genomics ($99-$349) fully sequences specific genes. Other companies, such as 23andMe ($199 for both health and ancestry information), use genotyping, which is more limited, to look for certain gene variants. Their BRCA1 and BRCA2 tests, for example, target three variants of more than 1,000 known to raise the risk of cancer. But – as the company makes clear in the results – testing negative for those variants doesn't mean a person lacks another harmful variant, and could lead to a false sense of security. Make sure you know how complete the test you're considering is.

Moreover, the most common diseases, including most cancers, are caused by a complex interplay of multiple genes and nongenetic factors. Genetic information may not add meaningfully to the risk details you can find from other sources. "All of this information needs to be put into the broader context of your health history, family history, environmental exposures and symptoms," says Amy McGuire, a bioethicist and lawyer at the Baylor College of Medicine.

If testing turns up something you want to act on, first talk to your provider. Even negative results are worth discussing. As FDA Commissioner Scott Gottlieb noted last year, "Consider the consequences of a person who is told they're not at risk for coronary heart disease and incorrectly opts to forgo dietary changes or drugs that reduce their risk of heart attack and death." If your test wasn't done in a clinical setting, your results may need to be confirmed – and the cost may not be covered by insurance. And doctors might not know what to do with information that has a modest or uncertain impact on your health.

The results probably won't make you anxious. When consumer genetic tests first hit the market, there was concern that learning about disease risk would spur anxiety, especially for diseases with no clear prevention strategy. That hasn't panned out, says Timothy Caulfield, a professor of law and public health at the University of Alberta in Canada. A 2016 research review found no increase in depression or anxiety in people who received personalized DNA-based disease-risk estimates. That's in the aggregate – some, of course, may stew more than others.

But results don't necessarily inspire behavior change. The same review found no significant effects of communicating DNA-based risk estimates on smoking cessation, diet, physical activity, alcohol use or sun-protection behaviors, for example. (Still, Francis Collins, National Institutes of Health director, has said he was inspired by direct-to-consumer genetic testing to lose 35 pounds after learning he is at higher risk of Type 2 diabetes.)

Not all of the claims are steeped in science. The FDA doesn't oversee the accuracy of gene-based tests that claim to predict your ideal diet, wine or romantic partner, which experts say have much less scientific backing than those that test for established genetic health risks. The bottom line: Some tests offer legitimate, actionable health information, says Megan Allyse, an assistant professor of biomedical ethics at the Mayo Clinic. Others offer interpretation based on less definitive science, or should be considered educational or "infotainment," she says. Eric Topol, a cardiologist, geneticist and researcher at the Scripps Translational Science Institute, sees the need in the marketplace for an independent evaluator to show whether the data and interpretation a company provides are accurate and useful. Until then: Proceed carefully.

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