Automated molecular testing of saliva for SARS-CoV-2 detection

Matic, N.; Lawson, T.; Ritchie, G.; Stefanovic, A.; Leung, V.; Champagne, S.; Romney, M. G.; Lowe, C. F.

Introduction: With surging global demand for increased SARS-CoV-2 testing capacity, clinical laboratories seek automated, high-throughput molecular solutions, particularly for specimen types which do not rely upon supply of specialized collection devices or viral transport media (VTM). Saliva was evaluated as a diagnostic specimen for SARS-CoV-2 using the cobas SARS-CoV-2 Test on the cobas 6800 instrument. Methods: Saliva specimens submitted from various patient populations under investigation for COVID-19 from March-July 2020 were processed in the laboratory with sterile phosphate-buffered saline in a 1:2 dilution and vortexed with glass beads. The processed saliva samples were tested using a commercial assay for detection of the SARS-CoV-2 E gene (LightMix) in comparison to the cobas SARS-CoV-2 Test. Results: 22/64 (34.4%) of the saliva samples were positive for SARS-CoV-2. Positive and negative concordance between the LightMix and cobas assays were 100%. There was no cross-contamination of samples observed on the cobas 6800. The overall invalid rate for saliva on the cobas 6800 (1/128, 0.78%) was similar to the baseline invalid rate observed for nasopharyngeal swabs/VTM and plasma samples. Conclusions: Saliva is a feasible specimen type for SARS-CoV-2 testing on the cobas 6800, with potential to improve turnaround time and enhance testing capacity.