Science and Tech


How Much Should You Trust Your DNA Test?

Direct-to-consumer genetic tests are a popular way to determine a person's ancestry and medical history. But how good are the results?
Posted at 12:29 PM, Jul 18, 2017

For the past 10 years or so, direct-to-consumer genetic tests have made determining your ancestry and predisposition to some diseases as easy as mailing a cotton swab of spit to a lab. But how reliable are they?

In some cases, it's hard to say what counts as accurate because the science isn't very precise to begin with. Ethnicity isn't determined by a specific gene, so the results actually show users where similar DNA has been found around the globe.

And for the few companies that do show their math, like, their sample sizes are relatively small. They divide the world into 26 genetic regions and use only 115 samples to determine what's representative of a specific region.

Other companies don't even publish how they get their results, making it hard to check their work. Each also relies on its own unique algorithms, so consumers could get different results depending on the company they choose.

That's why many personal genome service kits include disclaimers, like "for recreational purposes."

Regulating the industry hasn't been easy, either. In 2013, the Food and Drug Administration sent 23andMe a warning letter for failing to assure its product was "analytically or clinically validated" for diagnosing some diseases. It wasn't until 2017 when the company got some approval from the agency.

So, if you think you're in the market for a DNA test, the FDA and Centers for Disease Control and Prevention suggest meeting with a doctor.