Performance evaluation of Elecsys SARS-CoV-2 Antigen immunoassay for diagnostic of COVID-19.

Montalvo Villalba, María Caridad; Sosa Glaria, Elena; Rodriguez Lay, Licel de Los Ángeles; Valdés Ramirez, Odalys; García, Dayana Vallina; Arencibia Garcia, Amely; Martinez Alfonso, Javier; Menes Llerena, Dunia; Torres Pérez, Loida; Resik Aguirre, Sonia; Guadalupe Guzmán Tirado, Maria

INTRODUCTION One of challenge for control and prevention of SARS-CoV-2 infection is the early diagnostic at the point of care. Several tests based on qualitative antigen detection have been developed; one of these is Elecsys SARS-CoV-2 Antigen immunoassay (Roche Diagnostics). METHODS In total 523 nasopharyngeal swabs were randomly selected with the aims to evaluate sensitivity, specificity, cross-reactivity, positive and negative predictive value (PPV, NPV) and agreement of Elecsys SARS-CoV-2 Antigen immunoassay using RT-PCR STAT-NAT® COVID-19 as reference test. Cross reactivity was estimated using samples positive by RT-PCR to other respiratory virus (Influenza virus, Parainfluenza virus, Rhinovirus, Coronavirus OC43 and HKU1). RESULTS Overall sensitivity of Elecsys SARS-CoV-2 Antigen was 89.72% (288/321); specificity was 90.59% (183/202); and cross reactivity to other respiratory virus was not detected. Elecsys SARS-CoV-2 Antigen immunoassay showed a high sensitivity in samples with cycle threshold value <30, which ranged from 92.81% to 95.40%, independently of symptoms. PPV and NPV were 93.81% and 84.72% respectively. The kappa coefficient was 0.79 (95% confidence interval 0.73-0.84), showing substantial agreement between both tests. CONCLUSION The results suggest Elecsys SARS-CoV-2 Antigen immunoassay could be used as an alternative to RT-PCR testing, or in complement with it, to identify infectious individuals and reduce SARS-CoV-2 transmission. This article is protected by copyright. All rights reserved.