Recently, Time magazine listed the retail DNA test as its best invention of 2008 (thanks to Kevin M.D. for the tip). The best?  Maybe one of the most worrisome.

Time specifically highlights the do-it-yourself DNA testing kit from 23andMe, a California-based corporation named after the 23 pairs of chromosomes in each human cell.  The company sells $399 DNA kits that consist of a test tube in which you spit and send to the company’s lab. There, over the next 4-6 weeks, researchers extract DNA from your saliva and map your genome, putting the results online. You can access the results through the web and navigate a guide to your genes that estimates “[genetic] predisposition for more than 90 traits and conditions ranging from baldness to blindness.” 

Admittedly, this sounds pretty cool. As Time gushes, “in the past, only élite researchers had access to their genetic fingerprints, but now personal genotyping is available to anyone who orders the service online…” But look closer at the commoditization of DNA testing and the novelty wears off pretty quickly.

By pinpointing specific genes associated with certain diseases, a 23andMe gene read-out can inform a user of his or her susceptibility to those conditions. It turns out this is a lot less useful than it might seem. For example, Time reports that one test showed that the husband of 23andMe’s founder has a rare mutation that gives him an estimated 20 percent to 80 percent chance of getting Parkinson’s disease. The couple’s child, due later this year, has a 50 percent chance of inheriting this mutation, and thus his dad’s risk of Parkinson’s.

At this point, the parents-to-be have to worry that their kid will have
a mutation associated with an incurable disease. If he has it, they
also have to fret that he has anywhere from a one in five to a four in
five chance of actually contracting the disease. Really, how helpful
are these numbers? That’s a big range of probabilities. I wager it
doesn’t feel terribly good to be tracking the genetic lottery of your
son’s health, disease by disease.  In fact, I imagine that it’s
downright harrowing.

Dr. Alan Guttmacher, acting director of the National Human Genome
Research Institute of the National Institutes of Health, agrees. In
September, he told the New York Times
that “[DNA testing] can be neat and fun, but it can also have deep
psychological implications” because it can profoundly influence the way
we view ourselves, our loved ones, and our relationship to the world.
As Guttmacher told Time, “a little knowledge is a dangerous thing.”


Here Guttmacher isn’t just talking about the strange helplessness of
knowing the ever-so-approximate probability of your child getting sick.
He’s also speaking to the fact that DNA tests themselves only provide a
little knowledge—just one small piece of the complex puzzle that is our
health. Unfortunately, DNA tests often promise much more than this. One
company, Navigenics, is actually dedicated to reading your DNA and
diagnosing you with a set of medical risk factors that you then discuss
with an appointed “genetic counselor.” The idea is that genetic tests
reveal some sort of fundamental physiological truth; a complete and
comprehensive assessment of our health.

It’s true that some conditions, like cystic fibrosis and Huntington’s
disease, have been scientifically proven to be associated with
particular genetic mutations. But many other conditions have not been
shown to have a genetic origin—particularly when that gene is detected
without an intimate understanding of environmental factors surrounding
a patient, as it is the case when researchers on the other side of the
country analyze your spit. 

In light of this fact, the Genetics and Public Policy Center, a project of Johns Hopkins University and Pew Charitable Trust, warns
that many consumers “might have difficulty distinguishing between tests
widely used and accepted by medical professionals…and those whose
validity is unproven in the scientific literature.” Customers will see
their genetic print-out, with risk assessments for particular illnesses
tagged on each gene. But they won’t have a sense of how the DNA testing
company calculated that number—i.e. how much it reflects established
medical research or a best guess from a company trying to convince you
of its product’s predictive possibilities.

Unfortunately, the latter seems to be more plausible. In 2006, the Government Accountability Office (GAO) purchased
14 DNA tests from four different websites and sent in samples. The
office found that “the results from all the tests GAO purchased mislead
consumers by making predictions that are medically unproven and so
ambiguous that they do not provide meaningful information to
consumers.”

From GAO’s saliva samples, the companies sent back risk predictions for
conditions like diabetes and osteoporosis with little qualification,
even though “scientists have very limited understanding about the
functional significance of any particular gene, how it interacts with
other genes, and the role of environmental factors in causing disease.”
In other words, the tests were spitting out numbers and warnings even
though the genetic causality of these conditions “cannot be medically
proven.”

Further, many other results were all but “meaningless. For example,
[the companies reported that] many people ‘may’ be ‘at increased risk’
for developing heart disease.” But this is true for pretty much
everyone, “so such an ambiguous statement could relate to any human
that submitted DNA.” The laughable superficiality of the companies’
test results carried over into lifestyle information that GAO provided:
when the office told a company that the patient from whom the sample
derived smoked, the DNA company recommended that they stop smoking.
When the patient reported that he had quit, the company “gave
recommendations to continue to avoid smoking.” Gee, thanks—is that
really worth $400?

Ultimately, in the words of Dr. Muin Khoury, director of the National
Office of Public Health Genomics at the Centers for Disease Control and
Prevention, “the uncertainty [of medicine] is too great," to view DNA
testing as a sort of medical crystal ball. Even within the context of
our genes, the possibilities are endless. To its credit, Time
points out that “many diseases stem from several different genes and
are triggered by environmental factors. Since less than a tenth of our
20,000 genes have been correlated with any condition, it’s impossible
to nail down exactly what component is genetic.”

In fact, even when doctors do know that there’s a genetic component to
a given condition, they’re not always sure which genes to look at. For
example, in 2006 the Boston Globe noted
that “there are hundreds of mutations in two well-known breast cancer
genes, BRCA1 and BRCA2, for which reliable commercial tests exist. A
woman could be told that she didn’t have the common mutations but might
still be at high risk from less common mutations or a different gene
altogether…” Translation: even though we know there’s a genetic
component to breast cancer, it’s very difficult to pinpoint which gene
is the problem—particularly if the only way of communicating with a
patient about the issue is watered-down risk probability.

Meanwhile, the vagueness of DNA test results works in the favor of
testing companies. If they keep things simple and superficial, they can
make cross-promotion easier. In the GAO study, for example, the DNA
test results were synched with expanded product offers such as dietary
supplements, which had only a tangential relationship to the patients’
test results.

This sort of aggressive marketing is direct-to-consumer medicine at its
most profitable. Companies often want to convince patients that they
have a certain condition and then sell them on the cure. In
prescription drugs, this “disease mongering”
has usually been about listing symptoms to get people scared. But DNA
testing kicks things to another level: convince people that they are
actually hard-wired to contract a particular disease, and your cure
becomes that much harder to resist.

It’s no wonder that experts at Johns Hopkins are worried that
“advertisements may…underemphasize the uncertainty of genetic testing
results, or exaggerate the risk and severity of a condition for which
testing is available, thus increasing consumer anxiety and promoting
unnecessary testing.” Given what we’ve seen in direct-to-consumer
medicine up until now, this is a very reasonable fear.

Another plausible concern is that DNA tests, in their superficiality
and over-simplification of medicine, will be routinely misinterpreted
by patients. Time cites the case of Nate Guy, a 19-year-old in
Warrenton, Va., who “was relieved that though his uncle had died of
prostate cancer, his own risk for the disease was about average,”
according to his 23andMe test. This sounds uplifting until you realize
that, by the age of 70, the vast majority of men have prostate cancer.
Almost all of them will die with prostate cancer, not from it. (Something else will kill them before this very common, but usually slow-growing,
cancer catches up with them.)  An “average risk” of prostate cancer
means you’ll probably get prostate cancer and live with it for years,
just as do nearly all older men.

Presumably, Guy doesn’t know this. One gets the sense that he thought
his uncle died of prostate cancer because he died with prostate cancer,
and that this fact meant that his uncle had been uniquely susceptible
to the disease. Now Nate finds out he has an average level of
vulnerability and thinks that he won’t get prostate cancer.
Statistically speaking, none of this is probably true—but this is the
sort of reasoning that happens when patients are confronted with
misleading, sparse data about their health, devoid of a broader medical
context.

One can imagine that, had Nate been disheartened with the results of
his test, he would have similarly embraced the definitiveness of the
results and undergone unnecessary prostate screenings throughout his
life—screenings which have never been shown to actually improve
survival rates. Either way, Nate’s taking the wrong message from his
genome. Indeed, the likelihood that the patient will go for more
screenings—just to be safe—combined with the fact that people are
paying $400 a pop for a test which vaguely suggests whether they may or
may not contract a disease makes DNA tasting a profoundly
cost-ineffective health care option.

Genomics is a field that’s new and exciting; scientists will and should
pursue it. But it’s probably not something you should try at home.
From what we’ve seen so far, do-it-yourself DNA testing risks
exacerbating many of our most pressing health care problems: the
deceitfulness of for-profit medicine, the dangers of direct-to-consumer
health care, the glut of wasteful, potentially harmful, screenings, and
the general misconception that—if our gizmos are fancy enough—we can
all live forever.