ABSTRACT
Background-aim: Antibodies against SARS-CoV-2 detected by routine immunoassays ensure the existence of antibodies binding the virus, but not necessarily the elimination of the infection. Instead, neutralizing antibodies protect against SARS-CoV-2. Virus neutralization test remains the gold standard, but other neutralization assays have been developed to estimate the neutralizing potential against SARS-CoV-2, among them the FDA approved cPass SARS-CoV-2 Neutralization Antibody Detection (cPass) assay. We studied the correlation between the results obtained with SARS-CoV-2 IgG (Siemens Healthineers) and cPass (GenScript) assays in 218 patients. Methods: SARS-CoV-2 IgG is a 2-step sandwich immunoassay automated on Atellica analyzer. It is an assay based on indirect chemiluminescent technology used for the qualitative and quantitative detection of IgG antibodies (sCOVG) against SARS-CoV-2. cPass assay is a blocking ELISA detection assay using the HRP-conjugated recombinant receptor binding domain (RBD) from the viral spike protein and the human Angiotensin-Converting Enzyme 2 (ACE2). The interaction between HRP-RBD and ACE2 will be blocked if neutralizing antibodies against SARS-CoV-2 RBD are present in the sample. Results higher than 30% indicate the presence of neutralizing antibodies. Result: We observed that the presence of SARS-CoV-2 neutralizing antibodies correlated with sCOVG results, observing that neutralizing antibodies using the manufacturer cutoff (>30%) were present in 5% of samples with sCOVG <1, 83% of samples with sCOVG between 1 and 2, 96% of samples with sCOVG between 2,01 and 10, and 100% of samples with sCOVG >10. On the other hand we studied the agreement between the titers obtained for both tests using Passing Bablok regression analysis, obtaining a regression coefficient of 0.881. Finally, we compared the accuracy of the results of the sCOVG and the cPass tests. The area under the curve obtained in the comparison between both tests was 0,969. Furthermore, we observed a concordance between both tests considering the respective cut-off points (≥1 for sCOVG and ≥ 30 for cPass assay) in 96% of patients included in our study. Conclusions: We concluded that the Atellica SARS-CoV-2 IgG assay correlates well with the detection of neutralizing antibodies.