Variable Performance in 6 Commercial SARS-CoV-2 Antibody Assays May Affect Convalescent Plasma and Seroprevalence Screening

Abstract

Objectives Serologic detection of prior severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is needed for definition of convalescent plasma donors, for confounding SARS-CoV-2 presentation, and for seroprevalence studies. Reliable serologic assays with independent validation are required. Methods Six SARS-CoV-2 antibody assays from Beckman Coulter, Euroimmun (IgG, IgA), Roche, and Siemens (Centaur, Vista) were assessed for specificity (n = 184), sensitivity (n = 154), and seroconversion in a defined cohort with clinical correlates and molecular SARS-CoV-2 results. Results Assay specificity was 99% or greater for all assays except the Euroimmun IgA (95%). Sensitivity at more than 21 days from symptom onset was 84%, 95%, 72%, 98%, 67%, and 96% for Beckman Coulter, Centaur, Vista, Roche, Euroimmun IgA, and Euroimmun IgG, respectively. Average day of seroconversion was similar between assays (8-10 d), with 2 patients not producing nucleocapsid antibodies during hospitalization. Conclusions SARS-CoV-2 nucleocapsid antibodies may be less reliably produced early in disease than spike protein antibodies. Assessment of convalescent plasma donors at more than 30 days from symptom onset and seroprevalence studies should use assays with defined sensitivity at time points of interest because not all assays detected antibodies reliably at more than 30 days.

Analytical and diagnostic performances of a high-throughput immunoassay for SARS-CoV-2 IgM and IgG

“…Considering the cut-offs suggested by the manufacturer (i.e., 1.0 AU/mL for IgM and 1.1 AU/mL for IgG), the immunoglobulin rise could be considered significant seven days after fever onset. These findings are in agreement with those reported by us [2] and other Authors [6,16,17]. In addition, Kowitdamrong et al showed that seroconversion is fast in patients with Mod/Sev disease than in mild disease [16].…”

“…Second, COVID-19 convalescent plasma is one of the available treatment option and it is necessary to characterize the antibody response of each individual before accepting her/his for plasma donation [5]. Third, to assist in the diagnosis of patients who present later in their disease course or when the standard RNA detection methods are negative but clinical suspicion is high and other diseases have been ruled out [6,7]. Fourth, for epidemiological studies to determine seroprevalence in a population of high-risk subgroups of the population (e.g.…”

Suboptimal response to COVID-19 mRNA vaccines in hematologic malignancies patients

“…These results are expressed as extinction coefficient (signal/cutoff) ratios and are interpreted as positive (≥ 1.00), equivocal (> 0.80 to < 1.00), or non-reactive (≤ 0.80) 11 . Reactive results are confirmed by the Siemens SARS-CoV-2 Total Ig Assay, which detects both IgM and IgG antibodies against RBD of the S1 subunit of the Spike protein 12 . For analysis, reactive results were defined as positive, and equivocal or non-reactive results were defined as negative.…”

“…Among vaccine non-responders however, patients with CLL had significantly lower extinction coefficient ratios compared to those without CLL (median ratio 0.02 (range 0.02 – 0.06) versus 0.15 (range 0.02 – 0.91), respectively, p < 0.001) ( Figure 1B ). It should be noted that values below 0.10 are suggestive of no antibody response, whereas values closer 1.00 may suggest evolving or declining responses 12 .…”

Comparative Assessment of Sera from Individuals after S-Gene RNA-Based SARS-CoV-2 Vaccination with Spike-Protein-Based and Nucleocapsid-Based Serological Assays

“…In the course of the recent months, various studies have assessed the diagnostic performance characteristics of SARS-CoV-2-specific serological assays, indicating imperfect sensitivity and specificity of the assays, with higher reliability of assays targeting IgG compared to IgM- and IgA-specific ones [ 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 ]. Specificity problems with serological assays based on whole viral antigens [ 15 ] facilitated the development of more specific assays based on chosen structures of the virus only.…”