DNA Dilemma, Day Three: How Reliable Are At-Home DNA Tests?

courtesy of Mary Carmichael

In my weeklong quest to decide if I should have a genetic test, I now knew what I could expect to learn. But how was I going to feel about the results if I went forward and got them? Would I be able to trust them (and should I)? If I learned I had an increased risk for, say, Alzheimer's disease, would that be so upsetting that I'd rather not know? Was I the kind of person who could handle the results of a DTC test or even benefit from them, and did I need a doctor or counselor to help me process them? These questions were more personal than yesterday's—ultimately, I was going to be the only one who could answer them—but I needed some context to chew on. So I sought out five more experts:


Daniel MacArthur
Genetics research fellow, the Wellcome Trust Sanger Institute
"I'd suggest three rules of thumb. First, choose your company carefully: the major personal-genomics companies are generally reliable, but less reputable providers exist and should be avoided. Second, actively engage with your data: dig deep, read as much as you can, and ask questions about anything that doesn't make sense. Finally, don't place too much faith in any test result: consult an independent expert (a doctor or genetic counselor, in the case of health-relevant findings) before making any life-changing decisions.

Should you be scared of your results? The information you can get from genetic tests is so diverse, and different people will respond to their findings in different ways. My personal view: as a scientist, my desire for information—however incomplete and imperfect—outweighs my fear of the unknown. However, I appreciate that not everyone feels the same way!"

Read a longer version at Genomes Unzipped.

Mary's take: MacArthur knows quality control—he broke the 23andMe mix-up story on his blog—so I trusted him on that topic. I also appreciated that despite his own well-documented enthusiasm for DTC genetic tests, he wasn't pressuring me to take one. But I got a little stuck on his point about information, "however incomplete and imperfect." As a journalist, I want information to be "free," but I also want it to be right. How much imperfection could I tolerate in my own data? Was knowing about uncertainty enough to mitigate it?


Thomas Goetz
Executive editor, Wired magazine and author of The Decision Tree
"DNA might seem wrapped in mystery and intrigue, but genetic information is not so different from any other metrics we know about ourselves: age, weight, blood pressure. With scrutiny, any of these numbers can tell us something about our health and ourselves. It's the same with a genetic scan—it gives us some perspective, though far from the complete picture. Getting a scan today is the equivalent of buying the first-generation iPod. It will get much better as time goes on.

When it comes to choosing a service, beware the hype—those companies that promise to give definitive insight into the future, the 'if your kids have this gene they'll be Olympic athletes' sort of promises, as if our DNA were a crystal ball. The fact is, it's not. The legitimate services understand this and make it clear.

The fact that DNA is not destiny is, to me, a reason to consider getting a scan: understanding that we can act in response to our DNA, that we can change our lives to minimize the predispositions that our genes may create, should be a source of empowerment and reassurance."

Read a longer version at Goetz's blog.

Mary's take: I wasn't sure I agreed that a DNA scan would help me "minimize the predispositions" I have, since the scans give an incomplete assessment of those predispositions—and anyway, not all genetic tendencies are affected by lifestyle changes. Still, Goetz had a powerful point. I wouldn't be scared to learn my blood pressure. In fact, if it was an unhealthy number, I'd want to know so I could try to change it, or at least feel I'd been warned. Shouldn't the same be true of genetic data?


Henry T. Greely
Professor of law and director of the Center for Law and the Biosciences, Stanford University
"You can be confident you can't trust the results, because there's no consensus on interpretation, and personalized medicine isn't just about genetics. If your test shows you have a genetically low risk of lung cancer but you smoke four packs a day, your actual risk is much higher than average. Besides, will a 3.4 percentage-point difference in risk change your life—or be worth paying good money for? (Oh, and if you aren't of European ancestry, good luck getting any meaning out of these tests—the research behind the results was almost always done with white people.)

However, these companies do sell information on some powerful SNPs, such as APOE, linked to Alzheimer's disease, and BRCA1 and 2, linked to breast and ovarian cancer. Two smart and knowledgeable people, James Watson and Steven Pinker, both excluded only APOE from their public whole-genome sequences. Studies show negative psychological reactions are uncommon, but those studies included extensive genetic counseling—not required by these firms.

Knowledge can be powerful, both when understood properly and—dangerously—when misunderstood. If you test negative for those BRCA mutations, you might decide to avoid mammograms. That could be fatal. Not having those mutations lowers your genetic risk only from about 12.5 percent to 12.4 percent. As a first step the FDA should require that every health-related genetic test be prescribed by, and be returned through, your doctor."

Read more at the Center for Law and the Biosciences blog.

Mary's take: I knew Watson and Pinker had opted not to publish their APOE status. I, however, felt sure I'd want to know mine—if I'm at an increased risk for Alzheimer's, I want to cram as much as possible into my life before my mind starts going. Greely's point about BRCA ("12.5 percent to 12.4 percent"), however, left me disturbed. It seemed like the sort of thing a genetic counselor would explain. If I did take the test, I decided, I'd get someone to help me understand the results—but I wasn't sure that person needed to be a doctor.


Robert Green
Professor of genetics, neurology, and epidemiology, Boston University
"When we started the REVEAL study [of how people react to learning their risk of Alzheimer's disease], there was a strong sense that giving people information about a future disease that was not treatable would have devastating harm with no benefit. But we demonstrated that for those who specifically sought testing, there were substantive benefits and no short-term harms. We have also looked at some more subtle factors, such as how your perception of risk changes with data. For example, we published a paper that showed if you go in thinking you have a 30 percent or a 70 percent risk of Alzheimer's and you get told something very different, what you end up believing depends heavily on your initial self-perceived risk. People don't change their beliefs about their own risk on a dime.

With treatable diseases, can genetics be a motivational tool for doing what you ought to be doing anyway? The answer might be yes. But there's a dark side to that if you value genetic information as more deterministic than it is. If you learn you don't have any of the risk alleles for obesity, are you likely to reach for the jelly doughnut? We don't know. And misunderstanding genetic risk for a disease such as cancer may cause people to go through an extraordinary amount of surveillance, radiation, biopsies, worry, and expense. For each gene, each genetic risk, and each condition, we may have to ask: do the benefits gained by taking preventive measures or increasing surveillance balance out or exceed the potential harms?"

Mary's take: Green speaks with authority on how people react to learning about their genetic risks—he's one of very few people who've studied it in a randomized, controlled clinical trial. I was fascinated to know that (Watson and Pinker aside) a lot of people weren't bothered by learning their APOE status, since I thought I'd react that way too. But Green also had a disturbing point about overtreatment. A number of people had told me by this point that if I was concerned about any of my DTC results, I should get a doctor to confirm them. But that might lead to unnecessary tests, which in turn contribute to higher health-care costs. I've written about the overtesting phenomenon for NEWSWEEK many times. I don't want to exacerbate it.


Misha Angrist
Professor at Duke University Institute for Genome Sciences & Policy and author of the upcoming book Here Is a Human Being
"I worry that critics of consumer genomics start from the assumption that would-be participants don't know what they're getting into and ultimately cannot know, so, you know, let's call the whole thing off. If you believe, as I do, that genetics education is in a sorry state and must be fixed, then advocating willful ignorance for everyone is both logically and morally indefensible.

But like most activities in life, personal genomics is not for everyone. People who 'opt in' should know up front that these are still very early days. The ideal personal-genomics user is curious about the science, recognizes much of its tentativeness, and is an information seeker such that she won't shy away from information that may not bode well for her future health. Sending a company $400 and spitting in a tube is not the only way to get involved. There are a bevy of research studies that involve personal-genomic information. Take some time. See what's out there, what's involved, what your rights and responsibilities are, and what your expectations should be. This is your DNA and—unless you're an identical twin—no one else's. Don't be cavalier with it. Personal genomics is, finally, personal. Look in the mirror and decide what's right for you. Your feelings may be the exact opposite of mine. And that's fine: we shouldn't need each other's permission."

Mary's take: Angrist's advice was appealingly humane—unsurprisingly, since he was once a genetic counselor. I felt I fit his description of "the ideal personal-genomics user": curiosity and skepticism are two pillars of my value system (and my job as a science writer). I was glad he had pointed me toward other ways to engage with genetics than getting a DTC test. However, some of the projects Angrist linked to would give me less information than I'd get from 23andMe or deCODEme—and the point of getting tested, I thought, was to engage with information.

Read a longer version on Angrist's blog.

We're now on day three, and I still haven't come to a decision. However, working on this project has really changed the way I think about these tests and what it means to take or forgo one. Tomorrow I'll explore whether that decision should be mine alone, not mine at all, or mediated by a doctor—i.e., how should DTC tests be regulated?

Note: After this story was published, FDA press officer Erica Jefferson said that she, and not Elizabeth Mansfield, made the following comment: "And Mary, that cuts agency-wide. That is not considered in any of our reviews." Jefferson made no other comments during the interview.

Follow Mary on Twitter as she makes her decision, or add your opinion using the #DNADilemma hashtag.

DNA Dilemma: The Complete Series

Monday: Is Now the Time to Test?
Tuesday: What Can I Learn From This Test?
Wednesday: How Meaningful Are the Results?
Thursday: Should These Tests Be on the Market?
Friday: My Genome, Myself: I Make My Decision
Recommended Reading: Further Articles, Essays, and Web sites
DNA Dilemma FAQs: You're Doing What, Exactly?