Clinical performance and sample freeze-thaw stability of the cobas (R) 6800 SARS-CoV-2 assay for the detection of SARS-CoV-2 in oro-/nasopharyngeal swabs and lower respiratory specimens

INTRODUCTION: Studies describing the performance characteristics of the cobas®6800 system for SARS-CoV-2 detection in deep respiratory specimens and freeze-thaw stability are limited. The current study compares the clinical performance of the automated SARS-CoV-2 assay on the cobas®6800 system to a lab-developed assay (LDA) and the cobas impact of freeze-thawing combined with lysis buffer.

METHODS: Both retrospective and prospectively selected deep respiratory samples and oro- and nasopharyngeal samples in either E-swab® or GLY- were tested using the SARS-CoV-2 assay on the cobas®6800 System and compared to a lab developed assay. Additonally, SARS-CoV-2 RNA stability was assessed after one freeze-thaw cycle with or without lysis buffer.

RESULTS: In total, 221 (58.3 %) oro- and nasopharyngeal swabs, 131 (34.6 %) deep respiratory specimens, and n = 25 (6.6 %) swabs of unknown origin were included to study clinical performance. Only 4 samples gave discrepant results, all being positive in the LDA and not the cobas®6800 system. For stability testing, 66 samples without and 110 with lysis buffer were included. No clinically significant difference was found in test results after one freeze-thaw cycle and addition of lysis buffer.

CONCLUSION: Based on our findings, the cobas®6800 SARS-CoV-2 RNA assay yielded similar results as the LDA in oro-/nasopharyngeal swabs and deep respiratory specimens. Moreover, the cobas®6800 SARS-CoV-2 RNA assay yielded similar results before and after a freeze-thaw cycle, with better preservation of low viral loads in lysis buffer.