23andMe Testing Kit. (Photo: Frances Shaw)

With direct-to-consumer (DTC) genetic tests more in demand than ever, their accuracy has come under fire after a recent analysis. 

According to the analysis, about 40% of variants reported in raw data from DTC tests may well be wrong. The researchers from Ambry Genetics analysed how accurate the results actually are and soon discovered that two out of every five samples sent to them for confirmation testing were false positives. The study has been published in Genetics in Medicine

“Such a high rate of false positives in this particular study was unexpected,” explained first author Stephany Leigh Tandy-Connor, a genetic counselor at Ambry. “While DTC results may lead to healthy changes in lifestyle or diet, these could also result in unwarranted emotions, including anxiety when someone obtains unexpected information, inaccurate information, or disappointment when receiving a lack of comprehensive diagnostic analysis.”

There is such a growing interest among the public for these types of tests. Although they are not diagnostic, some firms will provide customers with their raw genotyping data, with a disclaimer. 

When carrying out the analysis, the researchers queried their internal database to identify patients who had been referred to them following DTC genetic testing. In fact, they uncovered 49 cases that came to them for confirmation testing between January 2014 and December 2017, largely for testing of cancer genes. For slightly more than half the cases, the variant of interest was provided to Ambry on a requisition form or in a clinic note, while more than 25% were from a DTC or raw data report, and the rest from a third-party interpretation service. 

The testing relied on either Sanger sequencing or next-generation sequencing followed by Sanger sequencing. The researchers were aware that the DTC firms use a wide range of methodologies. 

Overall, 60% of the variants Ambry analysed confirmed the DTC results, but the rest were false. It must be taken into consideration that the study was small, with a cohort of less than 50 people. However, Tandy-Connor suggested that this could be largely part to the fact that people don’t seek confirmatory testing. 

“People may assume that they are being provided accurate medical grade testing, so understandably do not go to the trouble and expense of seeking confirmation,” she concluded. 

If anything, the study’s findings highlight a need for these confirmations.