For a limited and accessible fee, interested consumers receive a kit to safely mail a saliva sample for testing. Then, they can receive back information about ancestry, paternity, ethnicity, and more individual characteristics, but also more “delicate” health-related results about carriage of alleles associated with an increased risk to develop a range of diseases. Of note, DTC-GT may specifically target either low-to medium risk alleles for common diseases (e.g.: ApoE4 genotype related to Alzheimer Disease), high-risk alleles (e.g.: BRCA1 variants related to breast and ovarian cancer), or provide more comprehensive studies such as whole exome and whole genome sequencing. Opinions regarding the usefulness and appropriateness of health-related DTC-GT vary widely across stakeholders. On the one hand, the knowledge of being at risk for certain diseases will result in preventive, pro healthy decisions decreasing health care costs, and can also facilitate the engagement of consumers in clinical research. On the other hand, tests without appropriate counseling can generate excessive anxiety and unnecessary medical exams and tests, potentially transforming healthy people in “pre-symptomatic patients” or so-called “patients in waiting”. Despite this controversy, DTC-GT is rapidly expanding with a significant budget growth in the next few years and a multiplication of new private companies riding the tide of DTC-GT. To assess the value of DTC-GT, we need to answer some critical questions, and have invited two experts in the field, Drs. Scott Roberts and Thomas Gasser for the discussion of this important issue.
What are the main concerns regarding the use of DTC-GT in Parkinson disease and other neurodegenerative disorders?
The vast majority of cases of Parkinson disease (PD) or other neurodegenerative disorders recognize a complex and multifactorial basis instead of pathogenic variants in a single gene (mendelian or monogenic). Most health-related DTC-GT offered on the market are focused on single-nucleotide polymorphisms (SNPs), which are associated with an increased risk to develop a common disease, and most of these explored genetic variants are known to make only a minor contribution to the development of complex disorders such as PD. Indeed, the detection of such risk variants in an individual has very limited predictive value since each variant is neither necessary nor sufficient for the disease to develop. In this context, the point is whether customers will be able to correctly interpret the outcome of DTC-GT and deal with its associated health risks. The concerns increase when dealing with neurodegenerative disorders lacking preventive treatments such as PD, and for tests such as WES or WGS that may detect “incidental findings” (variants increasing the risk to develop a disorder different from the one under testing).
Another major concern relates to the ethical aspects of the use, storage and protection of samples and data. Genetic privacy is undoubtedly a major issue about DTC-GT often in the absence of laws specifically protecting against the unauthorized use of genetic information. In fact, while the European Community established that genetic testing for healthy purposes can only be performed upon medical request and with appropriate counseling, DTC-GT may easily escape this rule. Indeed, a legal framework to protect consumers against stigmatization especially for some highly disabling diseases, and against potential discrimination by employers and insurers seems to be necessary because today DTC-GT by private companies remains largely unregulated.
How DTC-GT is perceived by the public?
DTC-GT is becoming very popular due to the strong argument of “empowerment” frequently used to increase its appeal to prospective customers. This refers not only to a hypothetical ability to make better health choices based on a deeper knowledge of genetic risks, but also to the perception of “being in control”. Additionally, a more widespread use of DTC-GT may be favored to help reduce the stigmatization that genetic information carries in many societies. From a different perspective, the increasing popularity of DTC-GT may also well relate to the increased medicalization and other changes in industrialized societies, as well as to novel social trends, such as “healthism” and network sociality. Yet, even for “actionable” genetic risks, the consequences for personal life style changes have been surprisingly low.
Certainly, the field of DTC-GT has a great potential for future expansion, but several crucial issues need to be resolved to the advantage of customers. As more people benefit from this affordable technology in the future, an increased level of integration with referring physicians is critical to interpret the test results in the frame of an updated scientific knowledge, and explain their actual relevance in predicting the disease risk, not only for the individual, but also for his close relatives
Dr. Scott Roberts
From the PGen study (“Impact of Personal Genomics” (PGen) study, a longitudinal survey of over 1600 consumers who undertook DTC-GT in the US), we were able to address a number of practical questions about the potential benefits and risks of DTC-GT. We observed that consumers generally understand the key health implications of DTC genetic testing results, although such understanding varies by consumers’ levels of numeracy and genetic literacy. Indeed, genetic test results are not only of interest to consumers in predicting future risk of disease, but also in helping to explain medical conditions that they already have. Also, DTC-GT results were found to be of special interest to adult adoptees, who often lack information about their family health history within their biological families. As to the interpretation of genetic test results, we observed that DTC testing prompted over a quarter of PGen participants to discuss their results with their primary care providers, but with highly varying levels of satisfaction. Yet, the likelihood of certain potential harmful responses to testing - such as overutilization of cancer screening tests and medication changes without physician consultation - was very low among study participants. Finally, and most importantly, it emerged that consumers perceive DTC-GT as potentially useful in informing future health decisions but often purchase test services without having considered the potential for unwanted results.
Dr. Thomas Gasser
Even though DTC genetic tests are becoming more and more popular in recent years, their level of integration with public health care still remains very low, with lack of connection to medical records and lack of physician involvement. In many cases, DTC-GT is purchased without the referring physician knowing about it, and even the results of these tests often are not discussed with a medical specialist. To date, most clinicians would agree on the fact that, in the absence of positive family history or specific clinical or laboratory “handles”, testing for genetic factors influencing the risk to develop PD or other neurodegenerative disorders is not recommended, due to the limited predictive value of these tests and the lack of established neuroprotective strategies.
On the other hand, as DTC-GT is in the world, it is crucial that movement disorders specialists and other physicians familiarize themselves with this method. They ought to be educated about concepts of genetic risks, particularly about the fact that current studies generally provide information about risk variants but rarely identify protective variants, which in an individual case may well balance a genetic risk. Because even if patients have sought DTC-GT without consulting a physician, they should at least be encouraged to do so later to help them to understand the results.
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