Are at-home DNA health tests accurate?

Two kinds of accuracy

Accuracy means two different things for a DNA test.

The first is technical: did the test find the right letters at each position? For the common positions a consumer array is designed to test, it usually does.

The second is meaning: does the result mean what the report says? A test can find a letter correctly and still draw a conclusion the research does not support. It can also report a rare variant it was never shown to detect reliably.

Do at-home DNA tests give false positives?

Yes, for raw health results, more often than most people expect. A study in the journal Genetics in Medicine looked at variants from consumer raw data that a clinical laboratory then retested. About 40 percent were false positives.

Most errors are in rare, serious variants. Arrays are built to test common ones.

The opposite error is a false negative. An array tests only the positions it was built for, about 0.02% of your DNA. If a relevant variant sits elsewhere, the report does not show it. A report with no findings can simply mean that position was never tested.

Confirm any serious finding with a clinical test before you act on it. A report with no findings applies only to the positions it tested.

Are 23andMe health reports accurate?

For ancestry and common traits, 23andMe and similar services are accurate and affordable.

Their health reports have the limits of an array. They cover a small, fixed set of positions. They miss rare variants outside that set.

Two things change how much a test can tell you. The first is how much of your DNA is tested, explained in Whole genome vs a DNA array. The second is whether someone checks the results against your own history.

In a Helixir report, a scientist checks every result, confirms the ones that matter and explains what they mean for you. How the analysis works.

Informational and educational, not a diagnosis. Bring anything of medical consequence to your physician.