No One Really Knows What Most Genetic Tests Mean
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Dr. Armstrong |
Genetic testing is all the rage. Thousands of tests are now available over the Internet, costing people anything from $60 to $3000 per test. While some DNA sequences are fairly well understood (like the BrCA gene or the chromosomal anomaly that causes Down’s Syndrome), most of them are only loosely associated with specific diseases and health outcomes. Experts agree that one day we’ll have a better understanding of the complex interplay of multiple gene sequences, but that day is still far off.
A recent post at GigaOM (h/t to KevinMD ) was critical of genetic testing in general, noting its potentially prohibitively expensive consequences:
Somewhere between 10 and 50 percent of autopsies reveal diseases other than the one that killed the patient. If consumers test themselves, then tell their doctors, the medical system could wind up treating 50 percent more diseases than it does today — even those that wouldn’t have killed the patient.
I interviewed Dr. Joanne Armstrong, senior medical director for Aetna, and assistant professor of obstetrics and gynecology at Baylor College of Medicine in Houston, Texas, about the current state of genetic testing. To listen to the full conversation, please click here.
Dr. Val: First of all, could you tell me a little bit about your work, and what got you interested in genetics in the first place?
Dr. Armstrong: I am the head of the Women’s Health division of Aetna, and about 8 years ago when BrCA testing (the test for predisposition to breast and ovarian cancer) became widely available, I began thinking about the educational initiatives that needed to support this testing. I knew that it would become part of mainstream medical practice and wanted to make sure that patients understood the tests and what to do about them.
Dr. Val: In your view, what are some legitimate and appropriate genetic tests?
Dr. Armstrong: There are about 1200 genetic tests available now, and most of them are not medically appropriate or clinically valid. “Medically appropriate” tests have a few common characteristics: 1) they have to be useful for the direct treatment or prevention of an illness. Some tests on the market are medically trivial – they test for things like eye color for example. 2) The information from the test should affect the course of treatment of the disease or condition, and 3) treatment should improve the outcome of the disease. Those are the characteristics of a genetic test that would be useful or appropriate in a healthcare setting.
There are 100s of useful and appropriate tests, and they’re used for the prediction of diseases like hereditary colon cancer, breast cancer and its recurrence, and metabolic diseases that affect people as infants.
Dr. Val: What are some inappropriate genetic tests that are being marketed? What makes them unhelpful?
Dr. Armstrong: There are many tests that suggest a genetic correlation with a disease outcome, but we have no idea exactly how it’s correlated. For example there are little sections of genes called “SNPs” (pronounced “snips”) that may be associated with diabetes, heart disease, or various types of cancer. However, these SNPs are just markers in a very large puzzle that includes lifestyle and behavioral choices. Just because a person has a particular SNP (associated with heart disease for example) in their DNA doesn’t mean they’ll develop heart disease. They may actually avert it with a healthy lifestyle and good nutrition. By contrast, a person who doesn’t have a SNP associated with lung cancer could still get it if they smoke.
When people receive a small piece of genetic information – disconnected from the whole genetic picture and their environmental risks, they can be misled to believe that they are doomed to develop a disease. That genetic information could be harmful in that it causes a lifetime of unnecessary anxiety. The flip side is that the absence of a certain SNP may be mistaken for immunity from disease, which could provide false reassurance and encourage people to discontinue preventive measures and screening practices for certain diseases.
The current environment of direct-to-consumer DNA testing is full of these kind of pitfalls, and I think it can be dangerous. The American College of Medical Genetics has established some minimal requirements for appropriate genetic testing.
Dr. Val: What are those requirements?
Dr. Armstrong: The requirements include 1) that the consumer should be fully informed regarding what the test can and cannot say about their health, and 2) a knowledgeable clinician should be involved in the process of both ordering the test and interpreting it. Interpretation can be very complicated because in many cases the science is not validated.
Interestingly, physicians report that they generally rate their own knowledge of genetics as “fair to poor” while consumers rate their knowledge of genetics as “poor.” So interpreting genetic tests really takes a specialist who is trained to understand exactly what the test means. Genetic counselors, board certified medical geneticists, medical oncologists, and some primary care physicians who choose to focus on this subject are well qualified to interpret test results.
Dr. Val: Is there a place online that people can go to to learn more about genetic tests and what they mean?
Yes, there are a number of good consumer sites. Aetna’s Intelihealth genetic guide is very helpful. It includes videos of hypothetical patients deciding if genetic testing is right for them. To find a genetic counselor, the National Society for Genetic Counselors has a good site. The National Institutes of Health has a great site called “understanding gene testing.”
Dr. Val: Is there anything I didn’t ask that you’d like to communicate to our readers and listeners?
Dr. Armstrong: I think genetic medicine will change the way medical care is fundamentally delivered. It will help us to understand our differences and provide personalized care to patients. Therapies could potentially become more effective and safer as well as more cost-effective. So these are very good things. This is the promise of genetic testing, but we really don’t have all the science needed to make informed decisions yet about a lot of the genetic tests that are available to consumers on the Internet. Of course, most physicians don’t feel prepared to fully explain or advise their patients on the results of genetic tests. So the best thing to do is to seek out a genetic counselor first if you’re considering genetic testing. That way you’ll be prepared to understand your results and take the appropriate next steps, if there are any.
To listen to a podcast of this discussion, please click here.
Excellent Interview,
Dr Armstrong said
“There are about 1200 genetic tests available now, and most of them are not medically appropriate or clinically valid. “Medically appropriate” tests have a few common characteristics: 1) they have to be useful for the direct treatment or prevention of an illness. Some tests on the market are medically trivial – they test for things like eye color for example. 2) The information from the test should affect the course of treatment of the disease or condition, and 3) treatment should improve the outcome of the disease.”
I disagree, most of the 1200 tests are clinically applicable. Also, a 4th characteristic: They are accurate ebough to plan future care and decisions……Insurers don’t see this as important, but as a patient and physician I sure do…..
-Steve
http://www.thegenesherpa.blogspot.com
http://www.helixhealth.org