Three types of potentially medically-relevant DTC-GT are available: (1) assessment of risk for common multifactorial diseases (e.g., diabetes, etc.); (2) targeted mutation analysis for single gene disorders; and, (3) sequencing. Some DTC-GT companies state that they do not guarantee the accuracy or reliability of their tests. Many of the significant genetic risk and protective factors for multifactorial conditions have not been identified. This leads to greatly divergent risk interpretations between companies, even when performed on the same individual. For targeted mutation analysis and sequencing, the specific test may not include all clinically relevant genes or mutations; resulting in false reassurance. Genetic changes that are only weakly associated with disease may be reported, leading to anxiety or inappropriate additional testing. When making medical decisions based on results of genetic testing, the test should meet the recommendations made by the Canadian College of Medical Geneticists in 2012. Not all DTC-GT meet these recommendations.
Sources:
Canadian College of Medical Geneticists. Direct-To-Consumer (DTC) Genetic Testing in This Country [Internet]. 2015 Jul 19 [cited 2017 Jan 3].
CCMG Ethics and Public Policy Committee, Nelson TN, Armstrong L, et al. CCMG statement on direct-to-consumer genetic testing. Clin Genet. 2012 Jan;81(1):1-3. PMID: 21943145.
Caulfield T, et al. Direct-to-consumer genetic testing – where should we focus the policy debate? Med J Aust. 2013 May 20;198(9):499-500. PMID: 23682895.
Peikoff, K. I Had My DNA Picture Taken, With Varying Results, New York Times [Internet]. 2013 Dec 30 [cited 2017 Jan 3].