Wendy Haaf answers your questions about health, nutrition, and well-being
Could a direct-to-consumer (DTC) genetic test such as 23andME provide me with potentially life-saving information about my health and risk for diseases?
It’s possible but very unlikely, according to Dr. Maha Saleh, the section head of Clinical Genetics at the London Health Sciences Centre and Southwest Regional Genetics Program in London, Ont. She says it’s rare for someone who’s taken one of these tests to get a result that needs to be acted upon—for example, by confirming it with clinic-based testing. What’s more likely is that someone who receives results free of red flags could be falsely reassured that they won’t get a disease. Knowing what type of technology a specific company uses and exactly what they use the test to look for can help you set realistic expectations about what you might learn.
Many consumer DNA tests “look for hot spots in one’s genetic material or DNA,” Saleh says. “We call them single nucleotide polymorphisms, or SNPs [pronounced ‘snips’].”
A company that uses this technology will focus on a list of specific SNPs. For instance, some companies test for a list of specific mutations on the BRCA1 and BRCA2 genes that are known to cause hereditary breast and ovarian cancers in families with Ashkenazi Jewish ancestry.
Say someone with a family history of breast cancer took one of these tests to gauge her risk for the disease and the results didn’t detect any of those BRCA mutations. That person might assume that she hasn’t inherited a genetic predisposition to breast cancer. However, she could have one of many less common mutations that aren’t covered by the test or even a mutation that’s unique to her family. “That’s where I worry sometimes about how some companies promote their product,” Saleh says.
It’s also worth pointing out that genetic tests can’t provide a yes-or-no answer about whether you’ll develop a given disease. For instance, even the BRCA mutations indicate only an increased risk for breast and ovarian cancers—a positive result doesn’t mean that someone will definitely develop the disease. Moreover, only five to 10 per cent of breast cancers are hereditary.
Before deciding whether to purchase a home DNA test, Saleh says, you should read the fine print. For instance, if it’s a SNPs-based test, which genes are being explored? Does the company provide scientific evidence linking specific gene variations to a given disease or trait? Is the lab conducting the test CLIA-certified—that is, has it met a set of quality standards?
Another important question, she adds, is “Who is sharing the results with you—is it a certified genetic counsellor?”
Since test results can be confusing, having a qualified professional help you interpret them is ideal, but most companies don’t offer this as part of their service.
But even before researching individual companies, you may want to read more about DTC genetic testing in general. For Saleh’s part, she believes that when it comes to getting answers about health, most often the results “end up causing more confusion than anything.”
