(Reuters Health) - Genetic tests sold online or in stores may produce false results, warn genetics experts in the UK.
When one of these tests indicates a “health risk,” it doesn’t necessarily mean someone will develop the health problem, and conversely, “reassuring” results may be unreliable, they caution in the medical journal BMJ.
“We had several people come to our clinic who appeared to have a genetic test result that put them at very high risk of developing a condition, for example, cancer,” said senior author Anneke Lucassen of the University of Southampton.
“When we checked their result with a more detailed technique, we found that it wasn’t there,” she told Reuters Health by email. “We then realized that colleagues across the country were coming across similar examples.”
Although most manufacturers warn against making healthcare decisions based on the results of direct-to-consumer (DTC) tests, some people do, Lucassen added.
“I think people often expect any genetic test to be clear cut,” she said. “The marketing around DTC tests suggests people will ‘find out’ about themselves and that results are accurate.”
Genetic tests often promise insights into ancestry, disease risks, personality or athletic ability, the authors write, but interpreting genetic information is complicated. Importantly, most direct-to-consumer tests don’t sequence the complete set of a person’s genes, or genome, and instead focus on specific variants in genes, which can lead to falsely positive results. Even tests that do sequence the full genome often identify variants that may not mean anything clinically, they point out.
Another limitation of these tests is that the prediction of a disease is often incorrect when there’s no family history of the illness. The authors describe a patient whose test, purchased online, indicated he had a gene variant that could increase his risk for Parkinson’s disease. He was upset, especially because he didn’t have a family history. In reality, many people carry genes that could increase their risk but have other genes that protect them from that risk, the authors explain.
False positives are common, too, the authors note. They tell of a patient who used an ancestry test and sent her raw genetic information to an online interpretation service, which told her she had a variant that could increase her risk of breast and ovarian cancer. Although she didn’t have a family history, she met with a breast surgeon and booked a date for surgery. She also met with a genetics scientist, who found she didn’t really have the variant. Her operation was canceled, but she still felt nervous about the possible risk.
“Some of the examples we came across were worrying because people were asking about risk-reducing surgery,” Lucassen said. “They thought they were at very high risk, yet such surgery would have been inappropriate.”
And reassuring results may be false negatives, the authors warn. One patient in her 40s with breast cancer and a family history of ovarian cancer took a test and was happy it showed no BRCA variants. Her doctor explained, however, that most tests only screen for a few variants. The patient then took an approved test, which found a variant that indicated a high lifetime cancer risk. Overall, patients with a family history of a disease should see a professional, the authors say.
“Even in our clinical practice, when someone has a personal or family history of inherited heart disease, it can be challenging to definitively attribute a genetic variant to disease in an individual or a family,” said Robin Hylind, a genetic counselor at Boston Children’s Hospital in Massachusetts. Hylind, who wasn’t involved with this article, tests for heart arrhythmias.
“DTC tests may fulfill an individual’s curiosity about ancestry,” she told Reuters Health by email. “However, they are not powerful enough to replace standard care at the present time, particularly in individuals with increased genetic disease risk.”
SOURCE: bit.ly/2pS15k3 BMJ, online October 16, 2019.