By Roy Benaroch, M.D., Emory University
There is a growing industry that uses broad genetic screening tests to look at hundreds or even thousands of genetic health risk factors. However, when reading media reports about this kind of testing, one should take into account the problems with the tests, as well as the caveats in the reports.
Are the Example Cases Relevant?
In the October 2017, The New York Times, published an article headlined “Personal Genetic Testing is Here. Do We Need It?” The tone of the article was set by the subheading: “Jody Christ, in her home in Elysberg, PA, says genetic testing saved her life, though experts warn such tests require caution.”
This article begins with a personal story, in this case, of a 62-year-old Jody Christ who struggled unsuccessfully for years to control her high cholesterol.
A genetic test revealed she had familial hypercholesterolemia, which put her at high risk for atherosclerotic heart disease, and she underwent a triple-bypass heart surgery. The article quotes Ms. Christ, “If I had not taken that test I might be dead by now.” That’s a dramatic and unequivocal endorsement of this kind of genetic test.
But this startling example isn’t a realistic example of the kind of genetic testing that the rest of this article talks about. Ms. Christ had intractably high cholesterol and testing revealed a definite, causal diagnosis. She needed to have been tested for arterial blockages anyway, even without the genetic test.
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From Science to Silly Stuff
The remainder of the article discusses testing on asymptomatic people, or people who don’t experience any health problems. And that kind of testing is very different.
Continuing from the Times article:
Experts […] also warn that some consumers may be led astray by genetic findings that are overblown or irrelevant. The Centers for Disease Control and Prevention, for example, takes a cautious approach to personal genomics tests, telling consumers on its website to ‘think before they spit’ and that ‘evidence on the ability of genetic information to change health behavior has been lacking.’
But that cautious sentiment is followed by a paragraph about a company offering testing for genetic variants “linked to” several kinds of cancer, or another test for heart problems. A medical officer at one of these companies says: “This is really for people who don’t have any reason to think that they’re at particular risk—but the problem is you really don’t know unless you do the genetic test.”
Some services, according to the article, claim to predict how well you’ll respond to different medications or even to different kinds of exercises, or which foods you should eat, or even which types of wine you might prefer.
So, the tests range from things that have at least some scientific support to claims that are just silly. Quoting a professor of genetics, the article says, “There’s this mixture of some that have real solid footing and then some that have zero footing.”
The Times article, though beginning with a personal endorsement, did at least superficially present a caveat, by covering the shortcomings inherent in the interpretation of these tests.
Learn more about how to better understand and evaluate medical data.
23andMe: Genetic Testing for the Consumer
A 2017 Huffington Post article focused on a different caveat that ought to be considered before testing. Titled “What to Consider Before Taking a 23andMe Test,” the thesis was revealed in the subhead, “You might not want to know all of your health results.” The title refers to testing by a specific company, 23andMe, which is one of the largest direct-to-consumer genetic testing companies.
The article begins in the first person, which is ordinarily taboo in traditional journalism, but gives the article a more personal touch.
I stared at the email announcing ‘Your 23andMe results are ready’ for several minutes before I had the courage to uncover my genetic health and ancestry secrets.
The article continues, talking about how more and more of these consumer genetic tests are likely to become available. The FDA has announced they’ve streamlined approval, and there are several new start-ups that are ready to offer testing for your risk of cancer, genetic diseases, and, quote, “an untold number of insights.”
Would You Like to Know Your Health?
A handful of labs are working on offering a very low-cost way to sequence your entire genome, perhaps for as little as $100, in the next few years. “Yet experts worry,” to quote the article directly again, “that consumers might be psychologically unprepared to handle frightening health information.”
This is especially true about tests for diseases that currently have no cure, like Alzheimer’s or Parkinson’s disease. In fact, the FDA approval of 23andMe’s health tests explicitly requires consumers to opt in to testing for these kinds of conditions.
Learn more about health, medicine, and the media.
Not Diagnosis, But only Risk Levels
And, again, there’s the crucial importance of understanding that these tests do not make a diagnosis. They can only predict a risk level. The Huffington Post article did say that toward the end, but what it didn’t say is that we cannot be sure of the accuracy of these risk estimates.
So what did the author’s testing show? The 23andMe material said she’d have a 5%-7% chance of having Alzheimer’s by age 75. But we should take a look at the context the article didn’t provide. According to the Alzheimer’s Association, the risk of having Alzheimer’s in the 65-74 year age range is between 3% and 9%. The evaluated risk is not much more accurate than the general estimate.
So, the media will often tell you the result of tests but not the complete context. The consumer and the reader should always know the caveats and the pitfalls.
Common Questions about the Caveats to Genetic Testing
The Centers for Disease Control is cautious about genetic testing because there is generally very little evidence about the ability of genetic information to change health behavior.
Some genetic testing services claim that their tests can predict how well an individual will respond to different medications or even to different kinds of exercise, or which foods you should eat, or even which types of wine you might prefer.
The FDA wants customers to opt in for genetic tests for diseases which have no cure or prevention, such as Alzheimer’s or Parkinson’s disease. This is because consumers might be psychologically unprepared to handle frightening health information.
