key: cord-326341-egtnqlov
authors: Liotti, Flora Marzia; Menchinelli, Giulia; Lalle, Eleonora; Palucci, Ivana; Marchetti, Simona; Colavita, Francesca; La Sorda, Marilena; Sberna, Giuseppe; Bordi, Licia; Sanguinetti, Maurizio; Cattani, Paola; Capobianchi, Maria Rosaria; Posteraro, Brunella
title: Performance of a novel diagnostic assay for rapid SARS-CoV-2 antigen detection in nasopharynx samples
date: 2020-09-23
journal: Clin Microbiol Infect
DOI: 10.1016/j.cmi.2020.09.030
sha: 
doc_id: 326341
cord_uid: egtnqlov

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to date the standard method in many clinical virology laboratories [1] . However, RT-PCR based 27 assays are labor-intensive and, when not completely automated, take hours to yield results. 28

Conversely, rapid antigen detection assays-intrinsically less laborious and requiring few minutes 29 to results-have the potential to satisfy the pressing demand for an early SARS-CoV-2 infection 30

Here, we evaluated the performance of the STANDARD F COVID-19 Ag FIA (SD Biosensor, 32

Suwon, South Korea) assay, a fluorescent immunoassay detecting SARS-CoV-2 nucleoprotein 33 antigen, on nasopharynx swab samples. It consists of a test device on which a pre-extracted sample 34 is allowed to react with a monoclonal anti-SARS-CoV-2 antibody and, after a 30-min incubation, a 35

Standard FX 2400 Analyzer instrument reads the intensity of fluorescence following the antibody-36 antigen complex formation. Initially, we determined the limit of detection (LOD) of the 37 STANDARD F COVID-19 Ag FIA assay by analyzing replicates of a dilution series containing 38

Vero E6 cell-cultured SARS-CoV-2 (INMI-1 strain) spiked in RT-PCR negative nasopharynx swab 39 samples at a 1.0 × 10 3 50% tissue culture infective dose (TCID 50 )/mL (4 × 10 6 RNA copies/mL) to 40 62.5 TCID 50 /mL (2.5 × 10 5 RNA copies/mL) concentration range. The LOD was 5 × 10 2 41 TCID 50 /mL (2 × 10 6 RNA copies/mL) at 95% detection probability ( Supplementary Fig. S1 Our study shows that the STANDARD F COVID-19 Ag FIA assay had a good specificity for 65 SARS-CoV-2 detection in nasopharynx swab samples but had a good sensitivity only for samples 66

with Ct values lower than 25 (corresponding to higher viral loads). Thus, we believe that the 67 STANDARD F COVID-19 Ag FIA (or similar) assays. This scenario would also encompass "new" 75 patients who begin their SARS-CoV-2 infection course with a low viral load (resulting in Ct values 76 of ≥35). In the light of these observations, it is presently difficult to envisage the correct, fruitful 77 and safe use of these assays unless they are integrated in laboratory diagnostic algorithms based on 78 both molecular and serological testing for SARS-CoV-2 infection. 79 assay. Probit analysis revealed a LOD of 5 × 10 2 TCID 50 /mL (2 × 10 6 RNA copies/mL) at 95% 110 detection probability. 111 

World Health Organization. Laboratory testing for coronavirus disease (COVID-19) in laboratory-2020.5-eng

Evaluation of a rapid diagnostic assay for detection of SARS-CoV-102 2 antigen in nasopharyngeal swabs

Evaluation of rapid 104 antigen test for detection of SARS-CoV-2 virus

First case of 106 2019 novel coronavirus in the United States