Inter-laboratory Agreement of Anti-Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) Serologic Assays in the Expedited College of American Pathologists Proficiency Testing Program.

Context - Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is a recently emerged, currently pandemic virus, and the etiological agent of coronavirus disease 2019 (COVID-19). Clinical testing for antibodies to SARS-CoV-2 has rapidly become widespread, but data regarding the inter-laboratory performance of these serologic assays are limited. Objective - To describe the development and initial results of the College of American Pathologists (CAP) SARS-CoV-2 Serology Survey. Design - Members from the CAP Microbiology and Diagnostic Immunology and Flow Cytometry Committees formed a working group to support development of a new proficiency testing survey for anti-SARS-CoV-2 antibody assays. Supplemental questions in the survey assessed the state of SARS-CoV-2 serologic testing among participating laboratories as of July 2020. Results were analyzed for agreement by immunoglobulin isotype tested, assay manufacturer, and methodology. Results - A total of 4,125 qualitative results were received from 1,110 laboratories participating in the first survey. Qualitative agreement for assays measuring anti-SARS-CoV-2 total antibodies or IgG was greater than 90% for all three samples in the survey. Qualitative agreement for IgM and IgA for the negative sample was greater than 95%, but lacked consensus for the other two samples. Conclusions - These initial data suggest overall excellent agreement and comparable performance for most qualitative anti-SARS-CoV-2 IgG and total antibody assays across all participating clinical laboratories, regardless of specific target antigen or assay methodology.