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Improving the Clinical Utility of DTC Genetic Tests

2018/11/1 9:05:35 Views:250
An estimated 100 million-plus people, roughly one-third of the U.S. population, will have had their DNA analyzed using an at-home genetic test kit by 2021. Up to 60% of the time, identified genetic variants are going to be proven correct with retesting in a medical-grade laboratory. For an investment starting at under $100, individuals can learn things that might save their life—or cause them to have unneeded treatments and surgeries—without a physician’s order for the test and often without follow-up of any kind by a healthcare professional.

There’s no use in physicians simply ignoring the soaring popularity of direct-to-consumer (DTC) genetic tests, says Emily Fine, a gynecologist in Hamden, Connecticut who is affiliated with Yale-New Haven Hospital. Ready or not, patients have started showing up at doctors’ offices with their 23andMe and Ancestry findings and possibly also beliefs about next steps from Dr. Google.

Fine believes that as DTC genetic tests become more popular and affordable, physicians ought to be proactively asking patients if they’ve had one done during routine exams—and then counseling them that it’s “only a first step” and to be sure they’re properly educated about what the results do and don’t mean, and the role of other factors (e.g., environmental and lifestyle) on disease risk. “A lot of my patients are already sharing that information with me,” says Fine.

“The problem with DTC genetic tests is that you can’t babysit ramifications of some of the information,” she adds. “I have a patient who found out she’s at risk for Alzheimer’s, and now she is profoundly depressed and every time she forgets where she put her keys she is ready to shoot herself.”

Fine’s preference is to understand patients’ pedigree or family history before ordering any clinically-indicated genetic test. But findings of DTC tests can sometimes also change her medical recommendations, she says. Recently, for example, a patient with a relatively weak family history of breast cancer discovered via 23andMe that she was of French-Canadian descent—an ethnic group that put her at heightened risk of several cancer-causing genetic mutations. That prompted Fine to refer the woman to have her entire cancer genome mapped.
The trouble is most physicians aren’t like Dr. Fine. They don’t understand genetics well enough to lead the conversation, if they have the time or even believe in the clinical utility of DTC consumer testing at all. “It is usually hard to get an appointment with a specialist based on 23andMe results,” notes genetic counselor Dawn Laney, director of the Emory Genetic Clinical Trials Center. Laney is also co-founder of ThinkGenetic, focused on educating bewildered patients and connecting them with personalized clinical genetic counseling and testing services.
23andMe findings are based on a SNP panel that offers an incomplete view of disease susceptibility, says Laney. To assess breast cancer risk, for example, 23andMe relies on three genetic markers in the DNA—including BRCA1 and BRCA2. Detected gene changes require follow-up in a diagnostic laboratory that specializes in breast cancer genes to determine if an individual’s lifetime risk is negligibly or profoundly higher than average. The opportunity for needless worry only multiplies when patients opt to receive all their raw uninterpreted genotype data from 23andMe and upload it to online portals such as Promethease for a personal DNA report.