Why Home DNA Tests Aren’t As Accurate As They Seem

Angela Cabotaje Fact Checked
© MEM Studio / Stocksy United

Do these stories sound familiar?

A young mom using a home DNA kit finds out she has an increased risk of developing Alzheimer’s disease. A man thinks he’s been living with undiagnosed celiac disease after taking a genetic test on a whim. A woman tries a food sensitivity test and finally gets answers about a mystery ailment she’s been suffering from since childhood.

The people and the circumstances are all different, but the marketing message is the same: Order a test online, take it in the comfort of your own home and learn more about yourself and your health.

It’s an empowering sentiment that direct-to-consumer genetic and health testing companies are using to sell their products. And it’s working.

The direct-mail health test business is now a multimillion-dollar industry. As of 2017, more than 12 million people had purchased consumer kits, which generally go for $200 a pop or less.

But are these tests as accurate and helpful as the commercials make them seem?

“As a general rule, I’d say, no. These tests are not effective and, in fact, they can be harmful,” says Fuki Hisama, M.D., medical director at University of Washington Medical Center’s Genetic Medicine Clinic. “I see patients who have had this testing, and they’ve misunderstood it, misinterpreted it and misdiagnosed themselves with conditions they do not have.”

“You could try two or three different consumer tests and have different results,” adds Robin Bennett, M.S., L.G.C., a senior genetic counselor at UW Medical Center’s Genetic Medicine Clinic. “These tests are fun and interesting, but that’s the only way they should be approached — as fun.”

The Centers for Disease Control and Prevention also cautions that these consumer tests have questionable validity and shouldn’t be taken seriously for health concerns.

Before we dive into why that is, let’s back up a bit to understand just what these tests are and how we got here.

Understanding direct-to-consumer health and genetic tests

Consumer DNA kits can be used for a variety of purposes, from genealogy discovery to genetic health testing, which scans for gene variants that can put you at a higher risk of developing certain diseases like breast cancer, Alzheimer’s or Parkinson’s.

Taking a home genetic test is often as simple as spitting in a plastic test tube and mailing your saliva back to the company. In a few weeks, you’ll receive a report noting any genetic risks, details about your general health and even some fun tidbits, like whether you’re more likely to hate cilantro or be afraid of heights.

Some companies even suggest specific fitness regimes or diets based on your genetic makeup.

Wellness tests, on the other hand, usually analyze a blood or urine sample to detect everything from food sensitivities and sexually transmitted infections to hormone and cholesterol levels.

So why are so many medical experts giving these direct-mail lab tests the thumbs-down?

Dubious testing methods and misleading results

“These tests should not be considered health tests because they have not been clinically validated,” Bennett explains.

Direct-to-consumer health tests don’t go through the same thorough lab analysis that ones ordered by your doctor do. Many of the kits you buy online only scan for a handful of gene variants out of thousands of possibilities. Or they use medically questionable testing methods.

A recent Los Angeles Times article detailed how a breast cancer survivor, who knew she had a BRCA2 gene mutation, took a consumer DNA test at home. Her results came back negative.

Hisama cautions that some people who take direct-to-consumer health tests are influenced by the results — despite any disclaimers the company includes — and don’t end up seeking professional genetic counseling or medical care that they actually need.

On the flip side, a study showed that 40 percent of variants reported in raw DNA data from direct-to-consumer genetic tests turned out to be false positives upon retesting in a clinical lab, leading to a whole lot of unnecessary anxiety and stress for the patients.

“The information these companies are providing to people is based on population databases, and there’s a lot of problems with that,” Bennett says. “Most of the controls and what’s deemed ‘normal’ are based on Northern European populations. If you’re African American or Asian or Hispanic, those results may not apply at all.”

Hisama and Bennett both say they’ve noticed an uptick in people calling in, worried about the results from a recreational genetic test.

“I think these tests are causing harm,” Bennett says. “The test may say you have a genetic risk of developing a disease but, in reality, it’s not different than the average person. But these tests feed that anxiety, and it’s hard as a healthcare professional to talk people out of a result that isn’t correct.”

Along with misdiagnosing people, consumer tests also don’t come with the same insight that only a doctor or genetic counselor familiar with your medical history can provide.

There are some companies that staff genetic counselors or doctors, but Bennett and Hisama say this doesn’t make those tests comparable to ones done with a medical professional who is knowledgeable about your background.

“We look at the context of your family history and your medical history,” Hisama says. “We do a complete evaluation; then we talk about your results. We disclose what this means for you, what it means about changes to your healthcare and what it means for your family members.”

The bottom line

Despite all the misgivings, there are some health tests you can take at home without any reservations. Things like pregnancy tests and evidence-based genetic studies, such as the MAGENTA study for ovarian cancer risk, fall beneath this umbrella.

Direct-mail tests for sexually transmitted infections are also useful, especially when it comes to providing you with a more discreet, convenient and affordable way to get tested.

That said, STI testing at a clinic still has some advantages over at-home tests. For one, if the results from a consumer test come back positive, you’ll still need to go to a doctor to get the results validated and receive medication. Getting tested at a clinic in the first place can speed up the treatment process.

Direct-mail tests also have more opportunities for user error. For example, some HIV tests won’t work until 10 to 90 days after an infection, depending on the type of test you take. If you take an HIV test at home without insight from your doctor, you may get false results that say you’re in the clear.

So what’s the bottom line?

“If you’re thinking about making a diagnosis or decision about medical treatment, please see a doctor or other qualified healthcare provider,” Hisama says.