SARS-CoV-2 RNA Quantification Using Droplet Digital RT-PCR.

Quantitative viral load assays have transformed our understanding of viral diseases. They hold similar potential to advance COVID-19 control and prevention, but SARS-CoV-2 viral load tests are not yet widely available. SARS-CoV-2 molecular diagnostic tests, which typically employ real-time RT-PCR, yield semiquantitative results only. Droplet digital RT-PCR (RT-ddPCR) offers an attractive platform for SARS-CoV-2 RNA quantification. Eight primer/probe sets originally developed for real-time RT-PCR-based SARS-CoV-2 diagnostic tests were evaluated for use in RT-ddPCR; three were identified as the most efficient, precise, and sensitive for RT-ddPCR-based SARS-CoV-2 RNA quantification. For example, the analytical efficiency for the E-Sarbeco primer/probe set was approximately 83%, whereas assay precision, measured as the coefficient of variation, was approximately 2% at 1000 input copies/reaction. Lower limits of quantification and detection for this primer/probe set were 18.6 and 4.4 input SARS-CoV-2 RNA copies/reaction, respectively. SARS-CoV-2 RNA viral loads in a convenience panel of 48 COVID-19-positive diagnostic specimens spanned a 6.2log

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Copyright © 2021 Association for Molecular Pathology and American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.