DTC Genetic Testing
By Robert Roth, M.D., Ph.D.
A year and a half after 23andMe received an FDA warning against selling its Personalized Genome Service genetic testing kit to consumers without marketing approval, FDA has authorized the company’s direct-to-consumer (DTC) test kit for identifying carriers of the BLM gene mutation causing Bloom Syndrome. FDA has decided this test kit can be considered a class II, exempt medical device without sufficient risks to require pre-market approval. This FDA decision means that consumers can directly determine whether they are asymptomatic carriers of the disease-causing recessive gene. If both parents have the mutation, passing the gene on to their children will cause Bloom Syndrome, a disorder with multiple physical and physiologic abnormalities including predisposition to cancer from sunlight and other UV exposures.
The Bloom Syndrome carrier test is entirely different from the more general Personalized Genome Service genetic testing kit that was pulled from the market, which promised data possibly predictive of late-onset diseases in the tested individual as well as carrier status information. The Bloom Syndrome carrier test is specific for disease linked to BLM gene mutations, and does not provide a broader assessment of single-gene clinical disorders that could be produced in offspring. However, many consider this test approval to be the first step toward a more comprehensive set of DTC genetic carrier assays which could eventually broaden the scope of genetic predisposition analysis and family planning.
The Bloom Syndrome carrier test is intended to provide consumers with genetic data which then would necessitate interpretation and explanation from genetic counselors. Although the accuracy of the genetic data is not considered an issue with this test and the results are considered reliable, the genetic information provided is likely to be confusing to many consumers without healthcare professional input. It has yet to be determined whether consumers will follow label directions correctly and appropriately close the loop with healthcare providers. Opponents to the availability of DTC genetic testing have concern that consumers might not follow such directions or might not even have a healthcare provider to approach for input. Opponents also fear the approval of the Bloom Syndrome carrier test begins the slippery slope toward the marketing of genetic predisposition of multi-factorial diseases, for which the exact contribution of an identified mutation to the overall risk of disease may not have been quantified.
Where does genetic carrier testing fit in with other mechanisms to predict and detect disease? On the one hand, carrier status screening and genetic counseling could lead to more effective prenatal diagnosis, and might avoid entirely the creation of an affected child as a reproductive option. Alternatively, knowledge of genetic predisposition could improve detection of disease in newborns before symptoms arise. Presently, only a small number of genetic disorders such as phenylketonuria, sickle cell disease, the thalassemias and a few other conditions are detected by routine, non-genetic newborn screening. In the event that a child is born with Bloom Syndrome, knowledge of this risk from carrier testing of the parents could identify the child as a cancer risk and a candidate for careful avoidance of known triggers such as excessive sun exposure.
Robert Roth, M.D., Ph.D. is the Vice President and Worldwide Medical Director at The Weinberg Group, the world’s leading food and drug consulting firm. If you have any questions or thoughts on this blog post or others, please contact us today.