Beware of False Results with Roche COVID-19 Test

False positive results associated with the Roche cobas SARS-CoV-2 (the virus that causes COVID-19) and influenza A/B nucleic acid test for use on the cobas Liat System may be related to two issues observed by Roche, FDA said.

Roche identified that the assay tubes may sporadically leak, causing an obstructed optical path in the Liat analyzer, producing abnormal PCR growth curves. This could lead to invalid or erroneous positive results, particularly for the Flu B test. If a tube leak occurs, later testing runs may have an increased likelihood of false positive flu B results. The company determined that abnormal PCR cycling in the reaction tubes may also produce abnormal PCR growth curves, leading to erroneous results.

FDA said the issue is sporadic and may be caused by multiple factors happening at the same time, such as hardware positioning, volume movement, and curve interpretation. The issue may cause false positive results for multiple analytes (flu A, flu B, and/or the COVID-19 virus) in a single testing run. False positive results could lead to improper patient management as well as unnecessary isolation and additional health monitoring, delayed diagnosis and treatment, and mis-allocation of resources used for surveillance and prevention for other infections or health conditions.

The agency reccomended that users of this test monitor for unexpected clusters of positive flu B results, as this may indicate the testing system has experienced a tube leak. Tests should be repeated when two or three analytes are positive, and different results on the repeat test may indicate abnormal PCR cycling, FDA noted. Labs that suspect either of these two issues have occured with their system should contact Roche.

FDA first authorized Roche's test for use in CLIA-certified labs in September 2020. The agency said it is working with Roche to resolve the two issues.

This latest alert puts Roche's test on a growing list of COVID-19 tests that have been flagged for potential false results. In January, FDA alerted patients and providers of the risk of false negative results with a COVID-19 test made by San Dimas, CA-based Curative, a startup that reportedly processes about 150,000 saliva samples daily and has a $42 million Department of Defense contract to supply its COVID-19 test kits to military treatment facilities.