Correlation between SARS‐COV‐2 antibody screening by immunoassay and neutralizing antibody testing

Abstract

Background The efficacy of convalescent plasma (CP), an alternative for the treatment of COVID‐19, depends on high titers of neutralizing antibodies (nAbs), but assays for quantifying nAbs are not widely available. Our goal was to develop a strategy to predict high titers of nAbs based on the results of anti‐SARS‐CoV‐2 immunoassays and the clinical characteristics of CP donors. Study Design and Methods A total of 214 CP donors were enrolled and tested for the presence of anti‐SARS‐CoV‐2 antibodies (IgG) using two commercial immunoassays: EUROIMMUN (ELISA) and Abbott (Chemiluminescence). Quantification of nAbs was performed using the Cytopathic Effect‐based Virus Neutralization test. Three criteria for identifying donors with nAbs ≥ 1:160 were tested: – C1: Curve ROC; − C2: Conditional decision tree considering only the IA results and – C3: Conditional decision tree including both the IA results and the clinical variables. Results The performance of the immunoassays was similar referring to both S/CO and predictive value for identifying nAbs titers ≥1:160. Regarding the studied criteria for identifying CP donors with high nAbs titers: (a) C1 showed 76.1% accuracy if S/CO = 4.65, (b) C2 presented 76.1% accuracy if S/CO ≥4.57 and (c) C3 had 71.6% accuracy if S/CO was ≥4.57 or if S/CO was between 2.68‐4.57 and the last COVID‐19‐related symptoms were recent (within 19 days). Conclusion SARS‐CoV‐2 IgG immunoassays (S/CO) can be used to predict high anti‐SARS‐CoV‐2 nAbs titers. This study has proposed different criteria for identifying donors with ≥1:160 nAbs titers, all with high efficacy.

Humoral immune response to COVID-19 mRNA vaccine in patients with multiple sclerosis treated with high-efficacy disease-modifying therapies

“…12 , 13 In the current study we used the Euroimmune ELISA assay to quantify SARS-CoV-2 antibody level as it was reported to highly correlate with the neutralizing antibody assay. 14 …”

Occurrence of BNT162b2 Vaccine Adverse Reactions Is Associated with Enhanced SARS-CoV-2 IgG Antibody Response

“…Only one individual among the questionnaire responders was previously diagnosed with a COVID-19 infection and was excluded. In addition, no quantitative analysis of neutralizing antibodies was performed, however, several studies showed a positive correlation between IgG against the receptor-binding domain (RBD) and neutralizing antibody titers [ 14 , 15 ].…”

SARS‐CoV‐2 antibodies: Comparison of three high‐throughput immunoassays versus the neutralization test

“…The same antibodies are also present in individuals once the SARS‐CoV‐2 infection is resolved, at levels that depend on the duration and severity of clinical symptoms 4 . The efficacy of passive antibody therapy has been associated with the concentration of nAbs in the convalescent plasma (CP) of recovered patients 5,6 . Thus, it would be useful to immediately identify donors with high nAbs titres.…”