Sars cov 2 igg assay

The IgG response against the S1 protein was measured by the SARS-CoV-2 IgG Assay (Siemens, Eschborn, Germany) and the total antibody response against the nucleocapsid protein by the Elecsys Anti-SARS-CoV-2 assay (Roche, Mannheim, Germany) according to the manufacturer's instructions. A semi-quantitative index of <1 was classified as negative, and a value of ≥1 or higher as positive. This cutoff for detection gives a specificity of 99.9% with a sensitivity of 96.4% for the Siemens spike assay.

To measure the IgG response against the S1 protein, we used the SARS-CoV-2 IgG Assay (Siemens, Eschborn, Germany). A semi-quantitative index of <1 was classified as negative, and a value of ≥1 as positive. This cut-off for detection gives a specificity of 100% with a sensitivity of 98% for detecting anti-S1 IgG antibodies. IgG response against the nucleocapsid protein was determined by the Elecsys anti-SARS-CoV-2 assay (Roche, Mannheim, Germany). Both assays were performed according to the manufacturer’s protocol.

Original manufacturer SARS-CoV-2 IgG assay (Siemens Healthcare Diagnostics Inc., USA) was used, and the serum samples were subjected to detection on ADVIA Centaur XPT system (Siemens Healthcare Diagnostics Inc., USA) for the presence of IgG antibodies against COVID-19 using a CLIA-based technique which is based on the fully automated two-step sandwich immunoassay using indirect chemiluminescent technology according to the manufacturer. The values of IgGs were expressed in cutoff index (COI), and a value of <1.0 was considered non-reactive, whereas COI >1.0 was reactive as described by the manufacturer’s manual.