A Novel Multiplex PCR Based Detection Assay Using Saliva or Nasopharyngeal Samples for SARS-Cov-2, Influenza A and B – Clinical Validation and Utility for Mass Surveillance
Abstract
Background
The COVID-19 pandemic has resulted in a significant diversion of human and material resources to COVID-19 diagnostics, to the extent that testing of viral pathogens normally contributing to seasonal respiratory tract infections have been markedly neglected. The global health burden due to influenza viruses and co-infection in COVID-19 patients remains undocumented but clearly pose serious public health consequences. To address these clinical and technical challenges, we have optimized and validated a highly sensitive RT-PCR based multiplex assay for the detection of SARS-CoV-2, Influenza A and B viruses in a single test.
Methods
This study evaluated clinical specimens (n=1411) that included 1019 saliva and 392 nasopharyngeal swab (NPS) samples collected in either healthcare or community setting. Samples were tested using two assays: FDA-EUA approved SARS-CoV-2 assay that targets N and ORF1ab gene, and the PKamp RT-PCR based assay that targets SARS-CoV-2, Influenza viruses A and B. The limit of detection (LoD) studies was conducted as per the FDA guidelines using SARS-CoV-2 and Influenza A and B reference control materials.
Results
Of the 1019 saliva samples, 17.0% (174/1019) tested positive for SARS-CoV-2 using either assay. The detection rate for SARS-CoV-2 was higher with our multiplex assay compared to SARS-specific assay [91.9% (160/174) vs. 87.9% (153/174)], respectively. Of the 392 NPS samples, 10.4% (41/392) tested positive for SARS-CoV-2 using either assay. The detection rate for SARS-CoV-2 was higher with our multiplex assay compared to SARS-specific assay [97.5% (40/41) vs. 92.1% (39/41)], respectively. The Ct values for SARS-CoV-2 were comparable between the two assays, whereas the Ct values of the housekeeping gene was significantly lower with multiplex assay compared to SARS-specific assay. The LoD was established as 60 copies/ml for SARS-CoV-2 and 180 copies/ml for Influenza A and B viruses for both saliva and NPS samples.
Conclusion
This study presents clinical validation of a multiplex PCR assay for testing SARS-CoV-2, Influenza A and B viruses, using NPS and saliva samples, and demonstrates the feasibility of implementing the assay without disrupting the existing laboratory workflow. This novel assay uses the same instruments, sample types, supplies, and laboratory personnel as needed for the testing of SARS-CoV-2 virus.
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