Commercial SARS-CoV-2 Molecular Assays: Superior Analytical Sensitivity of cobas SARS-CoV-2 Relative to NxTAG Cov Extended Panel and ID NOW COVID-19 Test

Link to article at PubMed

Jin R, et al. Arch Pathol Lab Med 2020.


Context - We implemented multiple nucleic acid amplification test platforms because of the limited availability of test kits for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) during the early stages of the pandemic. Interpretation of results generated by different platforms and prioritization for testing algorithms required cross-comparison. Objective - To compare the analytical sensitivity of three commercial SARS-CoV-2 molecular assays, selected samples were studied in parallel with Cobas SARS-CoV-2 test, NxTAG CoV Extended Panel, and ID NOW COVID-19 assays. Design - A total of 8043 SARS-CoV-2 tests performed from March 22 to April 19, 2020, were included in this study. For all 1794 positive specimens detected by the cobas SARS-CoV-2 assay, the cycle threshold (Ct) values were manually tracked and plotted, to demonstrate the distribution of sample viral levels. Additionally, 50 and 63 low positive specimens (Ct values >32) as well as 50 and 61 consecutive positive specimens by the cobas assay were tested with NxTAG and ID NOW, respectively, to estimate their relative sensitivities. Results - Ct values of cobas SARS-CoV-2 positive samples were evenly distributed over ranges of 13.32-39.50 (mean: 25.06) and 13.60-42.49 (mean: 26.45) for ORF1 and E gene targets, respectively. NxTAG only reliably detected specimens with E gene Ct values lower than 33, and is estimated to detect 89.4% of positive specimens detected by cobas assay. ID NOW had performance variation independent of Ct value and is estimated to detect 83.5% of cobas positives. Conclusions - Clinical specimens exhibit a wide range of viral burden, with a significant portion at low levels. Analytical sensitivity of testing platforms is critical for reliable detection of SARS-CoV-2 and uniform care to patients.

PMID:32649229 | DOI:10.5858/arpa.2020-0283-SA

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