Analytical performances of the point-of-care SIENNATM 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

Objectives: We herein assessed the analytical performances of the antigen-rapid diagnostic test (Ag-RDT) SIENNATM 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 suspected 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 SARSCoV-2 RNA, 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 K 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 SIENNATM Ag-RDT presents excellent analytical performances for viral loads <33 Ct, classically corresponding to situations of symptomatic COVID-19 and/or proven contagiousness. (c) 2021 The Authors. Published by Elsevier Ltd on behalf of International Society for Infectious Diseases. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Automated summary

The SIENNATM COVID-19 Antigen Rapid Test Cassette showed high sensitivity and specificity in diagnosing COVID-19 in hospitalized patients, especially effective for viral loads <33 Ct, indicating symptomatic COVID-19 and contagiousness.