Results from genetic testing kits that consumers can purchase online or in stores may be unreliable and should not serve as the basis for health care decisions, U.K. genetics experts warned in an editorial published in BMJ. Because these tests, such as 23andMe, do not take family history into account and only test for a few specific variants rather than sequencing the person’s full genome, both false positives and false negatives are possible.
“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 Anneke Lucassen, DPhil, of the University of Southampton. “When we checked their result with a more detailed technique, we found that it wasn’t there.”
On the other hand, false negatives may give false reassurance to patients. For example, the authors recounted the experience of a woman in her 40s with breast cancer and a family history of ovarian cancer whose direct-to-consumer genetic test showed no BRCA variants. Because most tests only screen for a few variants, the results of the test were misleading.
While direct-to-consumer genetic tests may be used to learn about the individual’s ancestry, the experts warn they are not a suitable replacement for genetic counseling with a professional.