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. 2021 May;100(1):115324.
doi: 10.1016/j.diagmicrobio.2021.115324. Epub 2021 Jan 23.

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

Nancy Matic  1 , Tanya Lawson  2 , Gordon Ritchie  3 , Aleksandra Stefanovic  3 , Victor Leung  3 , Sylvie Champagne  3 , Marc G Romney  3 , Christopher F Lowe  3
Affiliations

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

Nancy Matic et al. Diagn Microbiol Infect Dis. 2021 May.

Abstract

With surging global demand for SARS-CoV-2 testing capacity, laboratories seek automated, high-throughput molecular solutions, particularly for specimens not requiring specialized collection devices or viral transport media. Saliva specimens submitted from patients under investigation for COVID-19 from March to July 2020 were processed in the laboratory with sterile phosphate-buffered saline in a 1:2 dilution and tested using manual extraction and a commercial assay for detection of the SARS-CoV-2 E gene (LightMix®) in comparison to the Roche cobas® SARS-CoV-2 Test on the cobas® 6800 instrument. 34.4% (22/64) of saliva samples were positive for SARS-CoV-2. Positive and negative concordance between the LightMix® and cobas® assays were 100%. 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/viral transport media. Saliva is a feasible specimen type for SARS-CoV-2 testing on the cobas® 6800 platform, with potential to improve turnaround time and enhance testing capacity.

Keywords: COVID-19; SARS-Cov-2; automated; cobas 6800; saliva.

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Figures

Fig 1:
Fig. 1
(a) Mean cycle threshold (Ct) values for the Envelope (E) gene of SARS-CoV-2 in saliva samples showed close positive correlation between the LightMix® ModularDx SARS-CoV (COVID19) E-gene assay (TIB Molbiol; Berlin, Germany) and the cobas® SARS-CoV-2 Test (Roche Molecular Diagnostics; Laval, QC) on the cobas® 6800 platform. Five samples were excluded from analysis due to dilution that occurred prior to testing by the cobas® assay in order to increase sample volume. (b) Mean cycle threshold (Ct) values for the Envelope (E) gene of SARS-CoV-2 in saliva samples on the LightMix® assay and Orf1a gene on the cobas® assay showed close positive correlation. An additional 2 samples were excluded from analysis where the Orf1a target was undetected by the cobas® assay, but E gene was otherwise detected by both the LightMix® and cobas® assays.
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