Analytical performances of the point-of-care SIENNA™ COVID-19 Antigen Rapid Test for the detection of SARS‐CoV‐2 nucleocapsid protein in nasopharyngeal swabs: A prospective evaluation during the COVID-19 second wave in France

Mboumba Bouassa, Ralph-Sydney; Veyer, David; Péré, Hélène; Bélec, Laurent

Objectives We herein assessed the analytical performances of the antigen-rapid diagnosis test (Ag-RDT) SIENNA™ COVID-19 Antigen Rapid Test Cassette (Nasopharyngeal Swab) (Salofa Oy, Salo, Finland), targeting the SARS-CoV-2 N nucleocapsid protein, for the diagnosis of COVID‐19 in hospitalized patients with suspect SARS‐CoV‐2 infection, by reference to real-time RT-PCR (rRT-PCR). Methods Nasopharyngeal swabs were collected from patients with COVID-19-like illness during the second epidemic wave in Paris, France, among which 100 and 50 were positive and negative for RNA SARS-CoV-2, respectively. Results Overall, the Ag-RDT showed high sensitivity, specificity, positive and negative predictive values of 90.0%, 100.0%, 100.0% and 98.1%, respectively, as well as high or almost perfect agreement (93.3%), reliability assessed by Cohen's κ coefficient (0.86), and accuracy assessed by Youden’s J index (90%) to detect SARS-CoV-2. The analytical performances of the Ag-RDT remained high in the event of significant viral excretion (i.e., N gene Ct values ≤ 33 by reference rtRT-PCR), while the sensitivity of the Ag-RDT dropped to 69.6% with low or very low viral shedding (Ct> 33). Conclusions The SIENNA™ Ag-RDT presents excellent analytical performances for viral loads ≤ 33 Ct, classically corresponding to situations of symptomatic COVID-19 and/or proven contagiousness.