Performance evaluation of a Sars-CoV-2 rapid test and two automated immunoassays

Márcia J Castejon,Elaine L Oliveira,Cintia M Ahagon,Carmem Aparecida F Oliveira,Luís Fernando M Brígido,Rosemeire Yamashiro,Valéria O Silva,Marisa A Hong,Ana Késia S Lima,José Angelo L Lindoso,Edilene R P Silveira

doi:10.5935/1676-2444.20210040

Abstract

Due to urgency and demand of a response to the Covid-19 pandemic, numerous Sars-CoV-2 immunoassays have been rapidly developed. Objective: This study aimed at assessing the performance of rapid Sars-CoV-2 antibody test in comparison to high-throughput serological assays. Methods: A total of 86 serum samples were evaluated in the three assays: a lateral flow immunoassay - Wondfo Sars-CoV-2 Antibody Test (WRT) - and two chemiluminescence immunoassays: Elecsys Anti-Sars-CoV-2 (ECLIA), and Sars-CoV-2 IgG (CMIA-IgG). Results: The estimated diagnostic sensitivities of serological tests in the evaluation of serum samples from the epidemiological survey were: WRT 59% [95% confidence interval (CI) 43.4%-72.9%], ECLIA 66.7% (51%-79.4%), and CMIA-IgG 61.5% (47.1%-73%). Meanwhile, the estimated diagnostic specificity was for WRT 78.7% (95% CI 65.1%-88%), ECLIA 72.3% (58.2%-83.1%), and CMIA-IgG 76.6% (74%-95.5%). The sensitivity and specificity values were lower than manufacturers' claimed. Although 16.2% (14/86) of serological results were discordant among the three Sars-CoV-2 serological assays, the degree of agreement by the kappa index was adequate: WRT/CMIA-IgG [0.757 (95% CI 0.615-0.899)], WRT/ECLIA [0.715 (0.565-0.864)], and ECLIA/CMIA-IgG [0.858 (0.748-0.968)]. Conclusion: The serological testing may be a useful diagnostic tool, which reinforces its careful evaluation, and, as well as the correct time to use it. © 2021 Sociedade Brasileira de Pneumologia e Tisiologia. All rights reserved.

Highlights

Due to urgency and demand of a response to the Covid-19 pandemic, numerous Sars-CoV-2 immunoassays have been rapidly developed
The estimated diagnostic specificity was for Wondfo Sars-CoV-2 Antibody Test (WRT) 78.7%, ECLIA 72.3% (58.2%-83.1%), and chemiluminescent immunoassay (CMIA)-immunoglobulin class G (IgG) 76.6% (74%-95.5%)
16.2% (14/86) of serological results were discordant among the three Sars-CoV-2 serological assays, the degree of agreement by the kappa index was adequate: WRT/CMIA-IgG [0.757], WRT/ECLIA [0.715 (0.565-0.864)], and ECLIA/CMIA-IgG [0.858 (0.748-0.968)]

Summary

Introduction

Due to urgency and demand of a response to the Covid-19 pandemic, numerous Sars-CoV-2 immunoassays have been rapidly developed. Objective: This study aimed at assessing the performance of rapid Sars-CoV-2 antibody test in comparison to high-throughput serological assays. Methods: A total of 86 serum samples were evaluated in the three assays: a lateral flow immunoassay – Wondfo Sars-CoV-2 Antibody Test (WRT) – and two chemiluminescence immunoassays: Elecsys Anti-Sars-CoV-2 (ECLIA), and Sars-CoV-2 IgG (CMIA-IgG). Results: The estimated diagnostic sensitivities of serological tests in the evaluation of serum samples from the epidemiological survey were: WRT 59% [95% confidence interval (CI) 43.4%-72.9%], ECLIA 66.7% (51%-79.4%), and CMIA-IgG 61.5% (47.1%-73%). In cases with high clinical suspicion of infection with negative PCR results, antibody detection can be a useful tool to establish exposure, infection, and immunity to Sars-CoV-2, as well as to perform epidemiological studies[5, 6]. Compared to PCR, serological test is advantageous because of its faster turnaround time, highthroughput, less workload, and affordability of samples[3, 7]

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