Up to 40% of positive results in direct-to-consumer genetic tests are wrong, study suggests

Direct-to-consumer genetic tests may have a tendency to provide patients with false-positive results, according to a study published in the journal Genetics in Medicine March 22.

For the study, the researchers reviewed 49 patient requests for clinical confirmation of direct-to-consumer genetic test results, all of which had been flagged with genetic variants associated with a risk of disease. The 49 requests were submitted to Ambry Genetics, an Aliso Viejo, Calif.-based genetic sequencing company that processes DNA for medical and research institutions.

The eight study authors, all of whom are full-time employees of Ambry Genetics, determined 40 percent of variants reported in the DTC raw data were "false positives," suggesting the variant identified in the patient's initial test was not present.

The researchers also found clinical laboratories — including Ambry Genetics — classified some variants, which had been flagged with an "increased risk" classification in the DTC raw data, as "benign." The researchers determined these variants were benign based on analyses of publicly-available population frequency databases, which showed the variants tended to be common among patients.

The study authors noted these findings were based on raw genotyping data, rather than the refined data interpretations DTC companies present their customers. However, some companies provide customers their raw data, if requested.

"Our results demonstrate the importance of confirming DTC raw data variants in a clinical laboratory that is well versed in both complex variant detection and classification," the study authors concluded.

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