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Genetic testing is a popular way to get information on your ancestry. It can also alert you to possible disease risks.

However, “false positive” results from direct-to-consumer genetic tests are fairly common, a new study found.

Advances in genetic profiling and curiosity about ancestry have driven interest in the genetic tests offered by companies such as Family Tree DNA, My Heritage, 23andMe, and Ancestry.com.

The relatively low cost of the tests, which average around $150, has added to their popularity.

The Federal Trade Commission limits health-related claims in the way these reports are marketed.

However, companies that produce consumer-oriented genetic tests often allow the raw data from these at-home tests to be uploaded to third-party companies that offer to interpret the results for possible genetic health risks.

In a study published in the journal Genetics in Medicine, Stephany Tandy-Connor, an Ambry Genetics cancer counseling supervisor, said that 40 percent of health-related genetic variants analyzed in the at-home test data turned out to be incorrect.

“Such a high rate of false positives in this particular study was unexpected,” said Tandy-Connor. “While [direct-to-consumer test] results may lead to healthy changes in lifestyle or diet, these could also result in unwarranted emotions, including anxiety when someone obtains unexpected information, inaccurate information, or disappointment when receiving a lack of comprehensive diagnostic analysis.”

What the data revealed

The findings were based on an analysis of data from 49 at-home tests sent by consumers to Ambry for confirmation testing.

In some cases, the study said, the errors were made in the tests. In others, the analysis by third-party companies was faulty.

The researchers also noted that some genetic variants flagged as health risks in at-home tests or by third-party analysis companies are considered benign by Ambry and other clinical laboratories.

Tandy-Connor said the findings highlight the importance of getting the results of consumer genetics tests confirmed by a lab.

“People may assume that they are being provided accurate medical grade testing, so understandably do not go to the trouble and expense of seeking confirmation,” she said in a press statement.

Amanda Toland, PhD, a cancer researcher and genetic counselor at The Ohio State University Comprehensive Cancer Center, said false positive results in consumer genetic tests is “not unusual.”

“If you want to know what your genes tell you, you need to know that these tests really should not be used for medical decision-making,” Toland told Healthline.

She described at-home tests as broad but not deep. With the “hundreds of thousands of genetic variables they test, there’s always a small percentage that don’t work as well,” she said.

The testing done by clinical labs, on the other hand, is targeted at specific health conditions such as cancer.

A 23andMe spokesperson said that the company’s health data reports undergo “an incredibly rigorous, FDA-mandated accuracy review process” and have “demonstrated greater than 99 percent accuracy of testing results as compared to Sanger sequencing, which is considered the standard for analyzing DNA.”

“The study is being misinterpreted by many as a look at the information contained in our consumer reports, when in fact it was a look at how third parties analyze raw data files from several different companies,” a spokesperson for 23andMe told Healthline.

One person’s perspective

Julie Kennerly, PharmD, a pharmacist at the The Ohio State University Wexner Medical Center, took a 23andMe test along with her husband.

“We wanted to do it because it was fun but also for health screening purposes,” she said. “We wanted to be informed and take action if the test found anything.”

Kennerly submitted her 23andMe data to a third-party genetics analysis firm called Promethease.

Months later, the company told her that the results showed a high risk for a form of cardiomyopathy as well as Lynch Syndrome, a genetic condition linked with high rates of colon, ovarian, and endometrial cancer.

Kennerly sought out Toland for advice.

Confirmatory tests that cost her a few hundred dollars found that both results were false positives.

“I wish I knew that there was a huge rate of false positives because I probably would not have been as worried when I got the results back,” Kennerly told Healthline.

“I do think direct-to-consumer genetics tests should be available, but people need to understand that this is not a catch-all,” she added.

The false positive results cost her some money and a few anxious moments.

On the other hand, she said, “If this was a true positive, it could have been life-saving.”