Rapid differential diagnosis of SARS-CoV-2, influenza A/B and respiratory syncytial viruses: Validation of a novel RT-PCR assay.

BACKGROUND: Influenza and respiratory syncytial (RSV) viruses are expected to co-circulate with SARS-CoV-2 in the upcoming seasons and clinical differential diagnosis between them is difficult. Laboratory-based RT-PCR is a gold standard diagnostic method for influenza, RSV and SARS-CoV-2. The objective of this study was to estimate the diagnostic performance of a novel point-of-care RT-PCR assay STANDARD M10 Flu/RSV/SARS-CoV-2 (SD Biosensor) in a large number of clinical specimens with diversified (co)-infection patterns and viral loads.

METHODS: This was a retrospective study, in which all samples were tested in both STANDARD M10 Flu/RSV/SARS-CoV-2 index and Allplex SARS-CoV-2/Respiratory Panel 1 (Seegene) reference kits. Samples with discordant results were further processed in a third resolver test (Resp-4-Plex, Abbott).

RESULTS: A total of 1,019 naso-/oropharyngeal samples (50.3% positive for at least one virus) were processed in both STANDARD M10 Flu/RSV/SARS-CoV-2 and Allplex assays and the overall between-assay agreement was as high as 94.6%. Positive percent agreement of the STANDARD M10 Flu/RSV/SARS-CoV-2 was 100%, 96.6%, 97.3% and 99.4% for influenza A, B, RSV and SARS-CoV-2, respectively. The corresponding negative percent agreement was 99.7%. 100%, 100% and 98.4%, respectively. The expected positive and negative predictive values for all viruses were constantly above 96% in a reasonable range of disease prevalence.

CONCLUSIONS: STANDARD M10 Flu/RSV/SARS-CoV-2 is a reliable RT-PCR assay able to detect influenza A, influenza B, RSV and SARS-CoV-2 in one hour or less, fostering a rapid differential diagnosis of common respiratory viruses.