The US Food and Drug Administration released a letter on Friday warning clinical laboratory and point-of-care staff, as well as healthcare providers, that false positive results for Roche's test for SARS-CoV-2 and influenza A/B may occur.
The false positives for the Cobas SARS-CoV-2 & Influenza A/B Nucleic Acid Test, which is used on Roche's Cobas Liat system, could be related to two different issues raised by Roche, the FDA said. One is that the assay tubes might sporadically leak and cause an obstructed optical path in the Cobas Liat analyzer, resulting in abnormal PCR growth curves. This could cause invalid or incorrect positives, specifically for influenza B tests. FDA added that if a tube does leak, subsequent testing could have an increased likelihood of false positive results for Type B flu.
The other issue is that abnormal PCR cycling in the reaction tubes could produce abnormal PCR growth curves, causing false positives. FDA said the issue is sporadic and can be caused by hardware positioning, volume movement, and curve interpretation. The problem can cause false positives for any and all analytes in the run.
In the letter, FDA recommended people who are using the test should "monitor for unexpected clusters of positive Flu B results" and repeat tests when two or three analytes are positive, because different results on the repeat test could signal abnormal PCR cycling. If users expect either of the two issues to have happened, they should stop using the system and contact Roche, FDA wrote. The agency added that it is working with Roche to resolve the problems.
In an email, a Roche spokesperson said the company had recently identified "some erroneous results" with the test, specifically false positives, particularly in the Type B flu test, that had occurred sporadically. The spokesperson added that Roche is conducting an in-depth investigation to understand the cause and determine next steps, and proactively reported the events to the FDA.
Roche's test received Emergency Use Authorization from the FDA in September for use in moderate- or high-complexity labs and at the point of care. The test uses nasal swabs to differentiate viral nucleic acid from SARS-CoV-2 and influenza A and B and can return results in 20 minutes.
This article first appeared in our sister-publication, Genomeweb.