Opinion | Why You Should Be Careful About 23andMe’s Health Test

By The Editorial Board

Last month, the DNA-testing company 23andMe secured Food and Drug Administration approval for a new screening for gene-based health risks. Along with celiac disease, Alzheimer’s, Parkinson’s, breast cancer and several other medical conditions, the company can now screen clients for two mutations that have been linked to colorectal cancer.

But “F.D.A.-approved” does not necessarily mean “clinically useful.” 23andMe relies on much simpler technology than tests that you’d get at your doctor’s office. As a result, the company’s tests cannot tell you much about your actual risk of developing the diseases in question.

Here’s how those tests work — and why you should interpret them with caution.

That makes it difficult to draw conclusions from the 23andMe BRCA test. Just because you test negative for the few mutations that 23andMe screens for doesn’t mean that you won’t get breast cancer. It doesn’t even mean that you won’t get breast cancer caused by a BRCA mutation.

There are more comprehensive BRCA tests on the market. They require a doctor’s prescription, but they are much more useful, because they look at the entire gene. That means they give you a much better picture of the role that this gene might play in your overall cancer risk.

11 million

people with Ashkenazi Jewish

heritage can take 23andMe’s BRCA test

7.7 billion

people do not

have Ashkenazi

Jewish heritage;

the test is not

useful for them

2 percent

receive a

positive result

98 percent

receive a

negative result

Must confirm

results with a

clinical test

Results do not

rule out risk

11 million

people with

Ashkenazi Jewish

heritage can take

23andMe’s

BRCA test

7.7 billion

people do not

have Ashkenazi

Jewish heritage;

the test is not

useful for them

2 percent

receive a

positive result

98 percent

receive a

negative result

Must confirm

results with a

clinical test

Results do

not rule

out risk

23andMe’s other genetic health risk tests have the same shortcomings as its BRCA test: They look for only a handful of errors that may or may not elevate your risk of developing the disease in question. And they don’t factor into their final analysis other information, like family history. (Not everyone with a given mutation will go on to develop the disease.) So the results will not tell you much about your actual health risks.

The F.D.A. used to bar 23andMe from selling tests that purport to give health information because such tests were considered a flimsy predictor of health. Their results were also deemed too difficult for consumers to interpret on their own. The agency has since reversed that decision — in part because it has found the company’s tests to be accurate and its disclaimers clear.

23andMe has said that its health tests can raise awareness about various medical conditions and empower consumers to take charge of their health information. But doctors and geneticists say that the tests are still more parlor trick than medicine. Most of the diseases 23andMe tests for, including breast and colorectal cancer, are not primarily genetic. If you’re concerned about genetic susceptibility to cancer, Alzheimer’s or other serious conditions, it’s best to see a doctor.