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A conversation about the benefits and limitations of direct-to-consumer genetic tests

In this era of direct-to-consumer genetic testing, there are a number of products on the market promising to analyze a person's predisposition to disease or assist in determining a child's athletic niche. But a U.S. Food and Drug Administration panel and some members of the medical community have expressed concerns about the accuracy of such tests and potential dangers of individuals interpreting the results without consulting their health-care provider.

To better understand the potential benefits and limitations of direct-to-consumer genetic tests, I contacted Konrad Karczewski, a teaching assistant in Stanford's medical school course on personalized genomics. In the following Q&A, Karczewski provides an overview of the legal, ethical and social implications of genetic testing, why it's important to seek advice from both physicians and genetic counselors in interpreting test results and his experience studying his own genotype.

In the Stanford course, students were educated about the legal, ethical and social implications of genetic testing as well as the different kinds of commercially available tests prior to deciding to test their  genotype. Why it is important for individuals to understand these aspects prior to taking a test?

Genetic testing is a truly personal experience. It is an introspective  look at the reality of the traits, disease risk, and ancestry that an individual has inherited. Since it is personal in nature, individuals may have an emotional response both while considering the test and after reading the results, and so, it is important to understand what these results actually mean. Most notably, it is important to note that these results are not diagnostic, and as such, should not be taken as deterministic. The best these tests can do is adjust a probability that one will have a disease or trait. For some of the stronger associations, such as breast cancer, the choice whether to know may be difficult for some. However, whether or not you are aware of certain mutations does not change the fact that you have them, and therefore, individuals may prefer to be aware of them beforehand and be well-informed as to diagnostics, as well as possible prevention or treatment.

The disease risk descriptions on the testing companies' websites often have information pertaining to the disease and variants, as well as links to primary literature on the topic. GeneTests and GeneReviews, run by the National Center for Biotechnology Information, also have descriptions about the tests and diseases covered.

Additionally, since much of our DNA is shared with our family members, it is important to understand the implication of this test for them and what it means for their disease risks. Finally, discrimination based on genetic information for health insurance and employment is currently illegal in the United States, but individuals should be aware of the purview of the laws, as well as their rights.

Once individuals have a baseline education about the implications of genetic testing, who in the health-care community can help them understand or interpret the results?

After getting genetic tests, individuals should seek advice from both physicians and genetic counselors, if applicable. A genetic counselor can help interpret the results of a genetic test, but only a physician should provide medical advice in response to this test. While genetics provide a portion of the story, environmental and other factors also play a role in disease, and your physician can help integrate these factors together.

Critics argue that too little is known about the genes in the test panel used by these companies to reliably interpret the results. Is this true? What other limitations should individuals consider?

As with any genetic test, no set of genetic variants can definitively determine any specific disease or trait. In the case of athletic assessment, while certain genetic factors have been linked to performance, this does not translate to "if you have gene variant X, you will be good at sport Y." There exists a great deal of environmental factors in athletic ability and while genetic associations have been made, more studies must be done to determine whether a predictive model can be determined.

However, there is a great advantage in testing genetic factors associated with sport and fitness-related conditions, such as hypertrophic cardiomyopathy (HCM) and hemochromatosis. HCM is a major cause of sudden cardiac death in young athletes and with knowledge of the genetic risk for this condition, individuals could avoid excessive training. Not all genetic factors are known for these conditions, so individuals should be aware that other factors might still cause these conditions and not have a false sense of security. However, this information is still valuable, compared to not knowing and being blindsided by these conditions.

Given these limitations, what are the potential benefits to having your personal genotyping done?

For genotyping in general, despite the limitations, there is still much to be learned about disease risk, response to prescription drugs, as well as ancestry analysis. While use of genotyping as a routine clinical test is not widespread, understanding how your specific genetic variants influence your disease risk can enable awareness and possible prevention or treatment. Additionally, in a field known as "pharmacogenomics," an individual's response to certain drugs can be predicted by genetic factors and can aid a physician's decision to choose which drug or what dose of a drug to prescribe.

It’s been nearly a year since you participated in the Stanford class where you study your own genotype data. How has the experience affected your health-care decisions?

I am currently the teaching assistant for this year's course and my research is related to personal genomes, so this is something I think about all the time. Over the past year, I have watched my risk for various diseases go up and down with different interpretations. Because of this, my health-care decisions have not changed drastically, but I constantly explore my risk for diseases wherever possible and I have learned much by simply reading about diseases in the context of my own genotype.

Previously: Direct-to-consumer genetic testing: A commentary, Genotype testing for medical, graduate students, Stanford students discuss studying their own genotypes and Controversial class primes students in genomics
Photo by MIKI Yoshihito

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