At-Home DNA Tests: Are They Really as Accurate as They Promise?

Local experts weigh in on the usefulness of direct-to-consumer tests like Ancestry and 23andMe.



 

Samuel Armpriester was proving to be an elusive guy. He was born in 1843, but that was all Sydney Cruice Dixon could discover about her second great-grandfather. Dixon is president of the Greater Philadelphia Area chapter of the Association of Professional Genealogists and a member of the Main Line Genealogical Club. The Berwyn resident also teaches courses at the Historical Society of Pennsylvania. In researching her own kin, however, she’d hit a wall. “In records, I never saw him in any family group except with his wife,” Dixon says. “Who were his parents?”

Finally, Dixon found a probate record of a woman with the last name of Armpriester who died intestate. The court left the woman’s estate to her descendants, one of whom was her nephew, Samuel Armpriester. But were these the right Armpriesters?

Dixon turned to an at-home salvia-based DNA test. The results matched those of another Armpriester descendant, confirming the identity of Dixon’s second great-grandfather. Dixon also learned the name of Armpriester’s father, her third great-grandfather, and continued researching her lineage.

At-home DNA tests have become quite the fad of late. “But they can’t replace the records search,” says Dixon.

DNA can actually vary among cousins, and records tell stories that science can’t. “Knowing ancestors’ successes and failures connects us to them, personalizing their history,” Dixon says. “Those stories become part of us.”

Individual lineage is one part of at-home DNA tests; ethnic heritage is another. Results show the percentage of DNA associated with groups in various parts of the world. “The average person wants that cocktail-party ethnic pie chart,” Dixon says. “It purports to answer the question of where your people come from. But it’s the least reliable part of DNA results.”

The results are only as accurate as the population pool. How extensively do direct-to-consumer companies like Ancestry and 23andMe gather samples from various parts of the world? Some concentrate on the United States, others on Western Europe. As such, different companies will be of varying degrees of help, says Dixon. Researching them is critical to getting useful results. And be aware that DNA–with its Y, X, mitochondrial and autosomal genes–is incredibly complex. “Companies are trying very hard to make it simple for people,” says Dixon. “But there’s nothing simple about DNA.”

Dr. Susan Domchek couldn’t agree more. In March, the FDA authorized the analytic validity of a test run by 23andMe and other companies. That test screens for three BRCA genetic mutations linked to an increased risk for developing breast, ovarian and prostate cancer. They’re known as the Ashkenazi Jewish founder mutations because they’re prevalent among people of that heritage. “But more than 1,000 other mutations in BRCA 1 and 2 are associated with those cancers,” says Domchek, director of Penn Medicine’s MacDonald Women’s Cancer Risk Evaluation Center and executive director of Penn’s Basser Center for BRCA. “In addition, there are other genes associated with these risks of cancer. The testing offered there is incomplete.”

Domchek cited a recent study showing that when raw data was analyzed, the at-home tests were wrong 40 percent of the time. “Everyone’s goals are the same, which is to minimize barriers to genetic testing and maximum their utility for patients’ health,” she says. “But I’m a big believer that genetic testing is best done in the context of medical care.”

Dr. Terri McHugh is also skeptical of at-home tests. “They take advantage of people by making the process look easy,” says the co-director of Main Line Health Cancer Risk Assessment and Genetics. “At-home tests remove an important part: the genetic counseling piece. It’s critical for people to review family history, personal medical history, what the testing is for and how the results might impact their care.”

Domchek points out that, although genetic counseling is readily available in this region, it isn’t in other parts of the country. People also may think at-home tests are less expensive than their clinical counterparts. But many insurance plans will cover most of the medical costs.

Still, companies wouldn’t invest in cancer screening technology unless there’s consumer demand for the at-home tests. “If people are using direct-to-consumer options because they think it’s too hard to get genetic testing, then we need to fix that on our end,” Domchek says. “We want people to have the best, most accurate information so they can make the decision that is best for their health.”

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