Evaluation of High-Throughput SARS-CoV-2 Serological Assays in a Longitudinal Cohort of Patients with Mild COVID-19: Clinical Sensitivity, Specificity, and Association with Virus Neutralization Test

Abstract

Background The association between SARS-CoV-2 commercial serological assays and virus neutralization test (VNT) has been poorly explored in mild patients with COVID-19. Methods 439 serum specimens were longitudinally collected from 76 healthcare workers with RT-PCR-confirmed COVID-19. The clinical sensitivity (determined weekly) of nine commercial serological assays were evaluated. Clinical specificity was assessed using 69 pre-pandemic sera. Correlation, agreement and concordance with the VNT were also assessed on a subset of 170 samples. Area under the ROC curve (AUC) was estimated at 2 neutralizing antibody titers. Results The Wantai Total Ab assay targeting the receptor binding domain (RBD) within the S protein presented the best sensitivity at different times during the course of disease. The clinical specificity was greater than 95% for all tests except for the Euroimmun IgA assay. The overall agreement with the presence of neutralizing antibodies ranged from 62.2% (95%CI; 56.0-68.1) for bioMérieux IgM to 91.2% (87.0-94.2) for Siemens. The lowest negative percent agreement (NPA) was found with the Wantai Total Ab assay (NPA 33% (21.1-48.3)). The NPA for other total Ab or IgG assays targeting the S or the RBD was 80.7% (66.7-89.7), 90.3 (78.1-96.1) and 96.8% (86.8-99.3) for Siemens, bioMérieux IgG and DiaSorin, respectively. None of commercial assays have sufficient performance to detect a neutralizing titer of 80 (AUC<0.76). Conclusions Although some assays show a better agreement with VNT than others, the present findings emphasize that commercialized serological tests including those targeting the RBD cannot substitute a VNT for the assessment of functional antibody response.

Anti-SARS-CoV-2 seropositivity among medical students in Copenhagen

“…Among those positive, in the total Ig ELISA, around 76% were positive for IgG. We ascribe this discrepancy from the fact that the total Ig sandwich ELISA format provided by the Wantai system seems to be more sensitive than the direct IgG ELISA format as has been described previously 26 .…”

Longitudinal Analysis and Comparison of Six Serological Assays up to Eight Months Post-COVID-19 Diagnosis

“…However, the ABBOTT assay appeared to show lower performance, especially after 120 days. Other groups have already observed this phenomenon in an earlier post-PCR period [8,9]. At the end of the summer of 2020, ABBOTT defined a doubtful zone for the interpretation of its results, probably showing poor adjustment of their positivity threshold.…”

The Three Pillars of COVID-19 Convalescent Plasma Therapy

“…In addition, it is time-consuming (5-7 days) and non-standardized [15]. To overcome these drawbacks, several investigators have developed a number of immunoassays, such as enzyme-linked (ELISA) and chemiluminescent immunoassays (CLIA), as surrogate of PRNT [16]. Although such tests showed broad degrees of variability pertaining to the sensitivity and specificity when compared with PRNT, their diagnostic accuracy, which combines sensitivity and specificity and is represented by the area under the curve (AUC) in the non-parametric receiver operating characteristic (ROC) curve method, is often suboptimal [17][18][19].…”