FDA is alerting clinical laboratory staff, point-of-care (POC) facility staff, and health care providers that false positive results can occur with the Roche Molecular Systems’ cobas SARS-CoV-2 and Influenza A/B Nucleic Acid Test for use on the cobas Liat System. The false positive results may be related to two issues observed by Roche.

  • 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.
  • Roche determined that abnormal PCR cycling in the reaction tubes may also produce abnormal PCR growth curves, leading to erroneous results. 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. This issue may cause false positive results for multiple analytes (Influenza A, Influenza B and/or SARS-CoV-2) in a single testing run.

False positive results could lead to improper patient management. False positive results may also lead to unnecessary isolation and additional health monitoring, delayed diagnosis and treatment, and misallocation of resources used for surveillance and prevention for other infections or health conditions.


The FDA recommends users of the cobas SARS-CoV-2 & Influenza A/B Nucleic Acid Test for use on the cobas Liat System:

  • Monitor for unexpected clusters of positive Flu B results, as this may indicate the cobas Liat System has experienced a tube leak.
  • Repeat tests when two or three analytes are positive. Different results on the repeat test may indicate abnormal PCR cycling.
  • Stop using the cobas Liat System and contact Roche if you suspect either of these two issues has occurred.


The FDA authorized the Roche cobas SARS-CoV-2 and Influenza A/B Nucleic Acid Test for use on the cobas Liat System for use in laboratories certified under the Clinical Laboratory Improvement Amendments of 1988 (CLIA) to perform moderate or high complexity tests and at the POC in patient care settings operating under a CLIA Certificate of Waiver, Certificate of Compliance, or Certificate of Accreditation. FDA issued an Emergency Use Authorization (EUA) to permit emergency use of the test on September 14, 2020, and granted revisions to the EUA in September and December 2020.

Generally, the test is designed to detect and differentiate viral nucleic acid from SARS-CoV-2, the virus that causes covid-19, and influenza A and B viruses, in upper respiratory specimens, such as nasal swabs, from individuals suspected of respiratory viral infection consistent with covid-19 by their healthcare provider.

FDA Actions

The FDA is working with Roche to resolve these issues. The FDA will continue to keep clinical laboratory staff, POC facility staff, healthcare providers, and the public informed of significant new information.

Reporting Problems to the FDA

The FDA encourages users to report any adverse events or suspected adverse events experienced with the Roche cobas SARS-CoV-2 and Influenza A/B assay Nucleic Acid Test for use on the cobas Liat System.

Prompt reporting of adverse events can help the FDA identify and better understand the risks associated with medical devices.

Contact Information

Anyone with questions about this letter can contact [email protected].