A small study by scientists from a clinical genetic testing company found that at-home genetic testing kits misidentified risk factor genes 40 percent of the time – reporting that customers carried possibly disease-causing DNA sequence variations when in reality, the sequences were normal.
The results are a sobering reminder that direct-to-consumer (DTC) genetic analyses, as fun as they may be in telling us about our ancestry, are not accurate enough to provide medical diagnostic information.
As described in the journal Genetics in Medicine, the team reviewed sequence data from DTC tests performed on 49 individuals. In these cases, either the DTC company’s own report or that of a third-party interpretation service flagged the individual’s sequences as being potentially dangerous, and thus, the data was referred to Ambry Genetics for a thorough analysis. Among the 49 subjects, the DTC reports had identified a total of 26 pathogenic variants in genes for cancer, connective tissue disorders, cystic fibrosis, and familial Mediterranean fever.
DTC companies are not allowed by the Food & Drug Administration to market their services as diagnostic tests, yet some companies will give customers the raw data from analyses of selected genes associated with diseases. This data can then be further interpreted by third-party companies, often for a fee.
However, there are two big problems with this: First, DTC companies don’t actually sequence the entire genes associated with say, cancer or Parkinson’s disease. Instead, their tests look for the presence of single nucleotide alterations, called SNPs, that have been previously linked to the development of a disease. Second, DTCs don’t test within all the genes linked to these conditions, and variations in one alone may be safe.