key: cord-0717123-tmdqsemp
authors: Conklin, Justin; Arroyo, Jennifer; Kumar, Rajnish; Patibandla, Sai
title: Two SARS-CoV-2 serology assays detect antibodies in the sera of individuals diagnosed with SARS-CoV-2 Omicron variant
date: 2022-02-24
journal: Clin Biochem
DOI: 10.1016/j.clinbiochem.2022.02.010
sha: 7d66e884755b7c96c0a2626f72eb01c6a4683746
doc_id: 717123
cord_uid: tmdqsemp

nan

The Atellica ® IM SARS-CoV-2 IgG (sCOVG) and Atellica ® IM SARS-CoV-2 Total (COV2T) assays (Siemens Healthineers, Tarrytown, NY, U.S.) are semi-quantitative used for determining anti-S1 RBD IgG or Total (IgG and IgM) antibody levels, respectively. The sCOVG assay is a two-step automated sandwich chemiluminescent immunoassay. Recombinant antigens capture antibodies in the sample. After washing, mouse monoclonal anti-human IgG antibodies labeled with acridinium ester bind captured antibodies, generating a signal. The measuring range is 0.50-150 Index. The COV2T assay is a one-step (i.e., no wash step in between adding capture and detection reagents) automated sandwich chemiluminescent immunoassay that uses antigens to bridge antibodies. Recombinant antigens capture antibodies in the specimen. Recombinant S1 RBD antigen labeled with acridinium ester is added and binds the bound antibodies. The Results for the two assays are presented in Table 1 . The 10 samples were all reactive (positive) on the sCOVG and COV2T assays. Comparison of results with those for previous variants may indicate some reduction of signal, but the sample number was small. Nevertheless, sCOVG assay antibody levels (in WHO IS units, 83 to >1750 BAU/mL) were comparable to antibody levels (in BAU/mL) of another anti-S1-RBD IgG assay whose results corresponded to 60 to >80% vaccine efficacy; note, results were obtained pre-Omicron in 2020-2021 when efficacy was likely against infection by previous variants [5] . Study limitations included the small number of Omicron positive subjects and that we could not rule out concurrent or previous non-symptomatic and/or undiagnosed infections with other variants. Previous infections may have been detected if blood samples were obtained to test for antibodies when samples were collected for sequencing-although unlikely for all subjects. A concurrent infection could have occurred if subjects were infected with another variant shortly after, or on the day blood was collected for sequencing, and it is possible that we detected antibodies to that variant-again, unlikely for all subjects.

In conclusion, the sCOVG and COVT antibody assays appear acceptable for detecting antibodies in the sera of patients diagnosed with Omicron. Studies with more subjects are needed.

Author contribution: All authors contributed to conceptualization, experimental design, data collection and analysis, interpretation, and writing the manuscript.

Funding: This study was supported by Siemens Healthineers, Tarrytown, NY, USA 

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