Health & Wellness

What You Should Know About Commercial Genetic Tests

Here are the questions you should ask before you pay for a DNA test


By Wendy Haaf


If you’re curious about your ancestry or concerned about your genetic risk for certain health problems, you might have considered buying a direct-to-consumer genetic test. Before you pull out your credit card, here are a few things to think about.

What do I know about the company I’m considering?
This is one of the first areas to explore, according to Alexis Carere, president-elect of the Canadian Association of Genetic Counsellors and a genome analyst at the London Health Sciences Centre’s Molecular Diagnostics Laboratory, in London, ON.

“Is the company reputable? Do the results seem to be reproducible? There are a lot of reports of people getting a result from a direct-to-consumer company that turns out to be a mistake,” she explains. Since these things are tough for the average person to gauge, “you should look for companies that are better established,” she advises. As an example, she cites 23andMe. “They’ve been around a long time and they have been working with the US Food and Drug Administration,” she explains.

“The other thing to keep in mind is that different companies have different goals,” Carere adds. For instance, if you do some digging, you might find that a company you’re considering also sells supplements or other services, which can indicate a conflict of interest. “I might be more wary of that,” she says.

“I would also encourage people to find out if the company has someone who can answer questions. Is there a genetic counsellor or a physician on staff? Does the company have a sales rep who also does customer service? You need to be able to ask about the pros and cons of this testing and get an honest answer. And the same applies after testing: does the company offer support and guidance or does it just send you a report that says, ‘See your physician’? That’s important because it speaks to the reputation and reliability of the company.”

What am I hoping to learn?
There are companies that specialize in genealogy and others that provide information related to your health risks. But there are other, less obvious things to keep in mind, starting with the fact that “there’s a continuum of what’s reliable, what’s not so reliable, and what’s really not reliable,” says Paul Lasko, scientific director of the CIHR Institute of Genetics and a professor of biology at McGill University, in Montreal.

“The information that’s returned about ancestry and genealogy is pretty robust,” he says. “In the health area, the next most reliable is whether or not you’re the carrier of a disease whose primary cause is a single gene.”

In diseases such as Duchenne muscular dystrophy, for example, a person needs two “bad” copies of the gene in question to be affected. That means that if you have one bad copy “and you have a child with someone else who’s a carrier, there’s a 25 per cent chance your child will inherit two bad copies and be affected by the disease,” Lasko says. “We know about those mutations, and if the company is screening for those, then it can give you pretty robust information about whether or not you’re a carrier.

“The next kind of information some companies give you is predictions about whether you have an above-average or below-average chance of getting diseases such as heart disease and diabetes,” Lasko explains. Here, the water gets a bit murky.

Essentially, these predictions are based on studies that have found hundreds or thousands of genes that are more common in people with a particular condition than among those who are free of it. “So they can screen you and tell you that, of the 2,000 variants they’re looking at, you’ve got more than your share of the bad ones or more than your share of the good ones,” Lasko explains.

“Now, there’s probably some value in that information. On the other hand, any of these genes individually has essentially little or no effect on the probability of getting the disease, and we know very little about the cause-and-effect relationship,” Lasko says. “And when you look at the data, the differences in probability predicted aren’t all that high.” For example, consider a hypothetical disease that affects 10 per cent of the population: “If the test says you have a 20 per cent higher than normal risk, then you have a 12 per cent chance,” Lasko says. “And that estimate has a big error factor in it. So I don’t know how valuable that information is.”

Finally, at the opposite end of the credibility spectrum are companies that supposedly predict musical or athletic ability, or optimal diet or fitness plans based on your genes. “If those things have a genetic component, which is questionable, we’re decades away from understanding the genome well enough to make those kinds of predictions,” Lasko stresses.

Will the test give me too much or too little information?
“With health information, you need to think about what you’re trying to learn versus what you’re going to learn,” Carere says. “Say that you’re interested in your risk for heart disease because your father had a heart attack. If you do a test such as 23andMe, you’re going to get a lot of other information. Maybe you didn’t think through the fact that you’re going to get information about your risk for Alzheimer’s disease, and that’s something you actually wouldn’t have wanted to know, had you realized it ahead of time. So in a sense, there’s a risk of getting too much information.

“On the flip side, there’s the risk of not getting enough,” Carere continues. “The classic example is someone who says, ‘I’m really interested in my risk for breast cancer because there’s a strong history of breast cancer in my family.’” If that person doesn’t read the fine print, she may not realize that the commercial test screens for only three gene mutations of the many that have been linked with a higher-than-average risk of developing breast cancer. Consequently, when she receives a negative result for that part of the test, she may believe she’s free of any familial breast-cancer risk.

In that case, “you’re actually getting a lot less than you bargained for,” Carere says. If you have a strong history of breast or ovarian cancer, you’re better off speaking with your doctor: in most such cases, provincial health plans cover a referral to a genetic counsellor and, where appropriate, comprehensive genetic testing. “That’s going to be much more inclusive than anything you could order direct-to-consumer,” Carere says.

With ancestry tests, there’s also a question of whether you’re prepared for what you might learn—and what others might learn about you. “Keep in mind that you may learn some surprising information,” Carere notes. For instance, you might find a half-sister you didn’t know about from a parent’s prior relationship or secret affair. “These things can really shake up our understanding of our families,” Carere says.

“Another thing is that other people in the system may also find out about you,” Carere says. That’s something not everyone is comfortable with, for reasons ranging from safety concerns to an adoption they want to remain closed. “Check your privacy settings,” Carere counsels. “There are ways—it varies by company—to let them know you don’t want to be discoverable.”

How private will my data be kept?
“In theory, you’re sending the company your whole genome, no matter what they’re intending to look at,” Carere says. That means the company will have access to your complete genetic information. “Is the company going to analyze the whole DNA sample and report only a bit back to you? What is the company going to do with that data? Where are they going to store your DNA sample? Are they going to use the rest of the DNA for research? Are they going to use it to try to create new products? Can your data be bought, sold, or transferred?” Read the consent forms carefully to find out.

While there aren’t necessarily right or wrong answers to these questions, “You should look for a company that tells you how your DNA will be used and what restrictions can be placed on that,” Carere says, “and whether you could remove your DNA or change the conditions of your participation down the road.”

“There are some very interesting questions about who owns a person’s genetic information—questions that I think we’re still teasing out,” says Timothy Caulfield, the Canada Research Chair in Health Law and Policy and the research director of the University of Alberta’s Health Law Institute, in Edmonton.

What am I hoping to do with the health information I receive?
“If you’re thinking that taking this test is going to affect your medical care, I would advise speaking with your medical practitioner first,” Carere urges. “The reality is that a lot of these tests aren’t medically actionable.”

According to Caulfield, who is studying how direct-to-consumer tests are marketed, “Much of how the tests are being presented is in that the information will somehow empower you, that it will somehow allow you to lead a healthier life or adopt preventive strategies,” he says. “This is a very appealing narrative, but there are a couple of things wrong with it.

“First, we don’t change our behaviour based on genetic risk information,” he says. Then there’s the fact that, as noted earlier, outside of single-gene diseases, any increase in risk indicated by a test will be moderate. “And more important, I think, the preventive strategies provided are always the same, regardless of individual results: don’t smoke, exercise, and eat lots of fruits and vegetables,” Caulfield says. “That’s the ‘tailored’ advice I got from 23andMe for all my increased risks.”

Even so, people like Jen Costin, 41, of London, ON, feel they have gotten useful insight from a direct-to-consumer genetic test. Having lost two close friends to breast cancer, including one that was BRCA-related, Costin says she got “kind of paranoid” about her health, which ultimately led her to take the 23andMe test. The only health concern it revealed was an increased risk for blood clots—the cause of her paternal grandmother’s death in childbirth. With that information in hand, she can be more alert for the warning signs and promptly seek medical attention if necessary. “I feel a bit more comfortable.”

Photo: iStock/chromatika.