What Can DNA Home Tests Tell Us About Our Health?

Our genes can reveal a lot about us — where our ancestors come from, the color of our eyes and our risk for disease. Little wonder more and more Americans are sending off for at-home genetic tests that provide customers with all kinds of interesting information. In many cases, these tests become an inexpensive (and easy) way to check for potential genetic mutations.

But geneticists worry that such information might prove more troublesome than helpful, namely because these tests aren’t always accurate and the companies that provide the service aren’t as strictly regulated as medical labs that do genetic testing.

“What I usually tell people is that they can provide some limited information, but one needs the knowledge to interpret that information,” says Dr. Jeffery M. Vance, a neurologist with the University of Miami Health System and Dr. John T. Macdonald Foundation Department of Human Genetics. “There are different levels of accuracy on the technical aspect and [without the help of a properly-trained doctor, geneticist or genetic counselor] a person won’t know what it means.”

Millions of Americans have spit saliva and swabbed cheeks, mostly to find out about their ancestry. Bloomberg News reported that Ancestry.com alone sold 1.5 million genetic testing kits during Black Friday 2017 weekend. The industry itself grew from about $15 million in sales in 2010 to more than $99 million in 2017. Market-research company Kalorama Information projects it will reach $310 million by 2022. Interest had been stoked by the millions of dollars spent on marketing and advertising by companies such as 23andMe and Ancestry.com.

Lately, these direct-to-consumer tests have been in the headlines, as news outlets report how law enforcement officials have nabbed criminal suspects decades after the crime by using DNA information harvested by these companies from relatives. While this has prompted debate on privacy, worry about where information is stored and how it’s used doesn’t seem to bother consumers any, as about one-third of those surveyed in a recent NPR-Truven Health Analytics Health poll say they or a family member would consider getting a genetic test.

But here’s the problem:
A research paper published in Genetics in Medicine found that about 40 percent of consumers who are told they are at risk of a gene mutation eventually discovered that it was a false positive. The researchers reviewed the outcome of requests for clinical confirmation of direct-to consumer-genetic tests.

“False positives happen,” Vance concedes, “but this was much higher than I thought.” (23andMe responded in a long letter to the editor in the Genetics in Medicine journal, “23andMe has demonstrated the accuracy of our genotyping assay and the test results provided in our genetic health risk and carrier status reports through multiple, rigorous FDA reviews.” What’s more, it argued, the sample used for the study was small — 49 examples.)

Vance worries that if one of these direct-to-consumer companies does report a variation that can put a customer at risk of a disease, “it might be a huge cause of concern,” sometimes unnecessarily so.

“In order to get many diseases,” Vance adds, “many factors come into play. It’s not just one gene. You can have a risk gene but that doesn’t mean this particular gene will cause the disease. This can be confusing to people. I know it can be confusing for physicians who aren’t trained in genetics.”

Vance’s advice: Go see a medical geneticist or genetic counselor to give the results perspective and a plan of action.

False positives aren’t the only issue that worry geneticists. While Vance and others laud these home tests for their accessibility and their potential to alert consumers about possible health problems, he fears that such testing may lead people to mistakenly believe they are clear of developing a particular disease simply because they do not carry a very specific gene mutation. In other word, using results as the basis for health decisions is dangerous.

Vance points to the complex disease of cancer, specifically breast and ovarian cancer.  Earlier this year, 23andMe became the first direct-to-consumer company authorized by the FDA to test, without a prescription, three genetic variants found on the BRCA1 and BRCA2 genes known to be associated with higher risk for breast, ovarian and prostate cancer. Knowing you don’t have these variations, however, doesn’t mean a patient can breathe ease. Thousands of other mutations heighten the risk, as do lifestyle and environmental factors — none of which are tested.

“You can’t rule out anything with these tests just because you got a clean bill of health,” he explains.

Direct-to-consumer genetic testing is a relatively recent development. Before they hit the market, if you wanted a look at your genetic make-up, a doctor had to order such tests. They were expensive and hence, used sparingly, usually when the medical professional wanted to find out if a patient had a rare disease, was at risk of one, or at risk carrying a mutation that could be passed on to children.

Currently, the Food and Drug Administration restricts what these consumer testing companies can report about a client’s health. In fact, 23andMe displays this disclaimer visibly when a client checks on the health risk report: “Our reports do not include all possible genetic variants that could affect these conditions. Other factors can also affect your risk of developing these conditions, including lifestyle, environment, and family history.”

23andMe uses a sequencing technique that only tests for certain variants, not all. It looks at short pieces for DNA called single nucleotide variations that are linked to certain diseases. Other companies analyze every gene known to carry proteins that produce mutations, a process known as whole exome sequencing. But as Vance points out, only 2 percent of DNA make protein. (A third kind of test, and a much more expensive one, looks at the entire genetic code, but this whole genome sequencing requires a doctor’s order.)

To dig up more detailed information, some customers have been known to go the extra step by submitting the raw data from their direct-to-consumer analysis to yet other companies. These centers, however, are not always as sophisticated as some regulated medical labs, Vance says, as proven by the high false-positive study published in Genetics in Medicine.

“Technical accuracy can vary quite a bit,” he adds, “and they shouldn’t be regarded as conclusive.”

Nevertheless, Vance believes these tests have a place in our lives, particularly for those interested in their family heritage. If you’re worried about a family history of a disease, however, these home tests may, at best, be a starting point and, at worst, give you false worry or false relief. If you want a true review of your medical genetic risks, a test from a certified medical lab may put you back $2,000 to $3,000 or more.

He also suggests another alternative: The National Institutes of Health All of Us Research Program, which seeks to gather genetic data from one million or more people living in the United States to accelerate research and improve health by uncovering potential paths that can help deliver medicine tailored to a person’s genetic makeup.

Anyone over the age of 18 can join directly through the website or through participating health care provider organizations. The University of Miami Health System is one of 10 sites around the country selected by the NIH. The medical information gleaned from participants, who can then access their study results, will contribute to general knowledge eventually used by scientists in the program. Visit JoinAllofUs.org or allofus.nih.gov for more information as well as the University of Miami Health System.



In Their WordsAna Veciana Suarez
Ana Veciana-Suarez, Guest Contributor

Ana is a regular contributor to the University of Miami Health System. She is a renowned journalist and author, who has worked at The Miami HeraldThe Miami News and The Palm Beach Post. Visit her website at anavecianasuarez.com or follow @AnaVeciana on Twitter.