How Accurate Are Home DNA Kits?

DNA kits can dig into your ancestry or screen for potential health issues. (Photo: sdecoret/Shutterstock)

Last fall, I took a DNA ancestry test from MyHeritage and was surprised to learn that somewhere in my background I have Native American roots. That's nothing compared to the shock that Robyn Porter, a real estate agent from Maryland, uncovered when she took an AncestryDNA test and learned that her father was not actually her father.

Direct-to-consumer genetic tests have exploded in popularity in recent years. Now, you can use these tests to uncover not just your ancestry, but also any health issues that you may have now or in the future. But just how accurate are the results?

A recent study by Ambry Genetics (a clinical genetics-testing lab) found a 40 percent false-positive rate in the data from direct-to-consumer DNA tests. These results have many health experts crying foul over the availability and usage of home genetic tests without the guidance of a medical professional.

In the U.S., there are two main types of DNA tests available to consumers: those that reveal ancestry, like the tests that Porter and I took, and those that screen a person's DNA to reveal potential current and future health issues.

According to Nichole Holm, a Ph.D. candidate in genetics at the University of California, Davis, ancestry tests — even those with surprising results like mine and Porter's — are likely accurate. But Holm doesn't recommend using any kind of home DNA test in order to assess a person's health.

Issues with home medical genetic tests

Woman swabbing cheek for DNA test
At-home DNA kits typically use saliva or a swab a cells from inside the cheek. (Photo: Africa Studio/Shutterstock)

In March 2018, the Food and Drug Administration approved the direct-to-consumer DNA test from 23andMe to test for mutations in the BRCA1 and BRCA2 genes. Previous research has shown that these genetic mutations are linked to a higher risk of developing breast, ovarian and prostate cancer.

"While it sounds great to be able to do this on your own," Holm told MNN, "there are many problems with at-home medical genetic tests."

Holm explained that the error checking at a direct-to-consumer DNA lab is not as thorough as that conducted at a clinical lab.

"In order for a lab to provide medical advice trusted by a doctor, it needs to be CLIA certified, meaning that they promise to follow a list of rules and protocols to double-check everything they test and use," Holm said. Without this double-checking, mistakes can be overlooked and the results could be incorrect. That means that a home DNA test might incorrectly tell you that you don't need to worry about something, or make you worry about a result that may be inaccurate.

Direct to consumer DNA kits might also give consumers a false sense of security.

"23andMe only tests for three of the many different possible mutations," said Holm. "So if the result reports to the consumer that they do not have a BRCA mutation, that may not actually be true; it could just be that you do not have one of the mutations in their limited panel, which could then influence a person's choice in healthcare/prevention and urgency to go to a doctor."

On the flip side, just because you receive a result stating that you tested positive for a gene mutation, such as BRCA, it does not mean you will definitely develop the disease. "It means you are at a greater risk, and that risk should be explained by a trained professional like a genetic counselor," said Holm.

No help for next steps

Possibly the biggest issue surrounding at-home genetic testing is that consumers receive their results without the assistance of a doctor or genetic counselor to talk them through the next steps.

"These tests do not prepare individuals for the psychological impact of receiving the result that they may be at risk of a disease," said Holm. "Genetic counselors are trained to talk patients through the process, and ensure they understand the gravity and health options available to them. Without this, people can feel overwhelmed and confused with a disease-associated genetic result," she added.

Bottom line: If you want to know more about your heritage, home DNA kits are a good place to start. If you want to know more about your health, talk to your doctor first before you shell out for a genetic test that may or may not be accurate.