Title | Interpret with caution: An evaluation of the commercial AusDiagnostics versus in-house developed assays for the detection of SARS-CoV-2 virus. | ||
Author | Rahman, H; Carter, I; Basile, K; Donovan, L; Kumar, S; Tran, T; Ko, D; Alderson, S; Sivaruban, T; Eden, J-S; Rockett, R; O'Sullivan, M V; Sintchenko, V; Chen, S C-A; Maddocks, S; Dwyer, D E; Kok, J | ||
Journal | J Clin Virol | Publication Year/Month | 2020-Jun |
PMID | 32361322 | PMCID | PMC7195305 |
Affiliation + expend | 1.Centre for Infectious Diseases and Microbiology Laboratory Services, NSW Health Pathology-Institute of Clinical Pathology and Medical Research, Westmead Hospital, Westmead, NSW, 2145, Australia. |
INTRODUCTION: There is limited data on the analytical performance of commercial nucleic acid tests (NATs) for laboratory confirmation of COVID-19 infection. METHODS: Nasopharyngeal, combined nose and throat swabs, nasopharyngeal aspirates and sputum was collected from persons with suspected SARS-CoV-2 infection, serial dilutions of SARS-CoV-2 viral cultures and synthetic positive controls (gBlocks, Integrated DNA Technologies) were tested using i) AusDiagnostics assay (AusDiagnostics Pty Ltd); ii) in-house developed assays targeting the E and RdRp genes; iii) multiplex PCR assay targeting endemic respiratory viruses. Discrepant SARS-CoV-2 results were resolved by testing the N, ORF1b, ORF1ab and M genes. RESULTS: Of 52 clinical samples collected from 50 persons tested, respiratory viruses were detected in 22 samples (42 %), including SARS CoV-2 (n=5), rhinovirus (n=7), enterovirus (n=5), influenza B (n=4), hMPV (n=5), influenza A (n=2), PIV-2 (n=1), RSV (n=2), CoV-NL63 (n=1) and CoV-229E (n=1). SARS-CoV-2 was detected in four additional samples by the AusDiagnostics assay. Using the in-house assays as the "gold standard", the sensitivity, specificity, positive and negative predictive values of the AusDiagnostics assay was 100 %, 92.16 %, 55.56 % and 100 % respectively. The Ct values of the real-time in-house-developed PCR assay targeting the E gene was significantly lower than the corresponding RdRp gene assay when applied to clinical samples, viral culture and positive controls (mean 21.75 vs 28.1, p=0.0031). CONCLUSIONS: The AusDiagnostics assay is not specific for the detection SARS-CoV-2. Any positive results should be confirmed using another NAT or sequencing. The case definition used to investigate persons with suspected COVID-19 infection is not specific.