Evaluating direct amplification from viral transport medium for SARS-CoV-2 detection, strain typing, and angiotensin-converting enzyme genotyping and expression assays.

Abstract

Objective: The aim of this study was to compare the performance of direct amplification of viral nucleic acid from transport medium to extracted nucleic acid for polymerase chain reaction (PCR), sequencing, and genotyping applications.

Methods: XpressAmp lysate and extracted total nucleic acid from viral transport medium containing nasopharyngeal specimens were evaluated across different molecular applications to determine performance characteristics.

Results: SARS-CoV-2 quantitative PCR and angiotensin-converting enzyme (ACE) genotyping assays worked well with XpressAmp lysate, almost equal with or better than extracted nucleic acid in some specimens. However, XpressAmp completely failed to perform in next-generation sequencing for strain typing. Both protocols failed to detect ACE2 expression in viral transport medium.

Conclusion: Direct amplification of viral nucleic acid from viral transport medium containing nasopharyngeal specimen works well for molecular assays with low thresholds of quality; however, it does have limitations with assays that require high quality nucleic acid for input. Use of the XpressAmp protocol significantly improves turnaround time and allows for easy ramp-up of PCR and genotyping assays.