How Useful is the 23andMe Breast Cancer Test to You?

23andMe is one of a handful of genetic testing companies — they ship you a cotton swab, you send it back, and the company tells you about your ancestral makeup based on the results. Most of those companies, like Living DNA, stop there, but 23andMe has proven a bit more ambitious. They’re using that genetic information to screen for dispositions to certain diseases based on your genetic makeup, opening up a world of possibilities and pitfalls. Perfect example? This week, they secured FDA approval to use their home testing kit to screen for genetic markers that signal a higher risk of developing breast cancer. Sounds great, and it is, but the details of the 23andMe breast cancer test reveal how far home testing still has to go, and how important communication between companies and customers will be in the meantime.

The 23andMe breast cancer test checks for the presence of two genes, BRCA1 and BRCA2, that carry significantly higher risks of breast and ovarian cancer. However, the test only scans for three specific mutations of those genes out of thousands, limiting the number of women who will actually get useful information from the test.

Per a report from Scientific American, the genes are mostly found in women with Ashkenazi Jewish ancestry. However, only about two percent of that group has those three mutations in particular, with less than 0.1 percent of other women having the mutations.

In other words, for the vast majority of women, this test will not give any useful information about the likelihood of developing breast cancer or ovarian cancer. It could be an important and convenient screening test for women of Ashkenazi Jewish descent, but even then, the results will only be important if they do detect the presence of one of those gene mutations — per the Scientific American report, experts in the field are stressing that a negative result does not necessarily mean a low likelihood of developing one of those cancers.

It’s going to be very difficult for any company to create home testing kits that can help detect the cancer risk in large groups of people. Cancers have so many risk factors, both genetic and environmental — testing for just one or two risk factors only tells a small part of the story, making it difficult to draw any useful conclusions from negative tests. That will change in the future as companies like 23andMe develop tests for more risk factors, but developing and perfecting that many tests and getting them all approved by the FDA will take a lot of time. Until then, it’s not a bad idea to try out screening tests like these — they just won’t be the replacement for doctor’s visits and on-site tests (which are themselves seeing exciting developments) that many people are hoping for.

At the very least, 23andMe seems to have gotten a bit more responsible about taking things slow and making sure they have adequate scientific research to back their claims — in 2013, the FDA ordered 23andMe to stop giving out health information using their genetic testing, claiming the company had not been meeting the FDA’s standards throughout the approval process. The test approved this week had been part of those reports before 2013. They’ve since worked with the agency and resumed issuing health reports in 2015, but only as they secured FDA approval for their tests. It’s a good thing — the intersection between the slow-moving healthcare world and the fast-paced consumer technology industry can end up being disastrous for customers. Just ask the people behind Theranos.