Sensitivity of SARS-CoV-2 antibody tests with late convalescent sera (preprint)

SARS-CoV-2-specific IgM antibodies wane during the first three months after infection and IgG antibody levels decline. This may limit the ability of antibody tests to identify previous SARS CoV-2 infection at later time points. To examine if the sensitivity of antibody tests falls off, we compared the sensitivity of two nucleoprotein-based antibody tests, the Roche Elecsis II Anti-SARS-CoV-2 and the Abbott SARS-CoV-2 IgG assay and three glycoprotein-based tests, the Abbott SARS-CoV-2 IgG II Quant, Siemens Atellica IM COV2T and Euroimmun SARS-CoV-2 assay with 56 sera obtained 6-8 months after SARS-CoV-2 infection. The sensitivity of the Roche, Abbott SARS-CoV-2 IgG II Quant and Siemens antibody assays was 94.6 % (95% confidence interval (CI) 85.1-98.9 %), 98.2 % (95% CI: 90.4-99.9 %) and 100 % (95% CI: 93.6-100 %). The sensitivity of the N-based Abbott SARS-CoV-2 IgG and the glycoprotein-based Euroimmun ELISA was 48.2 % (95% CI: 34.7-62.0 %) and 83.9 % (95% CI: 71.7-92.4 %). The nucleoprotein-based Roche and the glycoprotein-based Abbott RBD and Siemens tests were more sensitive than the N-based Abbott and the Euroimmun antibody tests (p=0.0001 to p=0.039). The N-based Abbott antibody test was less sensitive 6-8 months than 4-10 weeks after SARS-CoV-2 infection (p = 0.0002). The findings show that most SARS CoV-2 antibody assays correctly identified previous infection 6-8 months after infection. The sensitivity of pan-Ig antibody tests was not reduced at 6-8 months when IgM antibodies have usually disappeared. However, one of the nucleoprotein-based antibody tests significantly lost sensitivity over time. Highlights Most antibody tests correctly identified SARS CoV-2 infection 6-8 months after infection The sensitivity of the antibody tests was 48.2-100 % The three tests with the highest sensitivity (94.6-100 %) were the N-based Roche and the RBD-based Abbott and Siemens assays The N-based Abbott IgG CMIA was significantly less sensitive 6-8 months than 4-10 weeks after infection (p = 0.0002)

Correlation of ELISA based with random access serologic immunoassays for identifying adaptive immune response to SARS-CoV-2 (preprint)

Public health emergency of SARS-CoV-2 has facilitated diagnostic testing as a related medical countermeasure against COVID-19 outbreak. Numerous serologic antibody tests have become available through an expedited federal emergency use only process. This paper highlights the analytical characteristic of an ELISA based assay by AnshLabs and three random access immunoassay (RAIA) by DiaSorin, Roche, and Abbott that have been approved for emergency use authorization (EUA), at a tertiary academic center in a low disease-prevalence area. The AnshLabs gave higher estimates of sero-prevalence, over the three RAIA methods. For positive results, AnshLabs had 93.3% and 100% concordance with DiaSorin or Abbott and Roche respectively. For negative results, AnshLabs had 69.7% and 73.0% concordance with DiaSorin and Roche or Abbott respectively. All discrepant samples that were positive by AnshLabs and negative by RAIA tested positive by all-in-one step SARS-CoV-2 Total (COV2T) assay performed on the automated Siemens Advia Centaur XPT analyzer. None of these methods, however, are useful in early diagnosis of SARSCoV- 2.