• Justin Manalac, Jennifer Yee, Kyle Calayag, Linda Nguyen, Payal M Patel, Daniel Zhou, and Run-Zhang Shi.
• Clinical Chemistry and Immunology Section of Clinical Laboratories, Stanford Health Care, United States.
• Clin. Chim. Acta. 2020 Nov 1; 510: 687-690.

BackgroundWe report our findings of test performance especially specificity of a fully automated Abbott Architect anti-SARS-CoV-2 CMIA IgG and Euroimmun anti-SARS-CoV-2 ELISA IgA/IgG in human plasma.MethodsWe used positive cohort of 97 samples from Covid-19 patients or healthcare workers, collected at late time points from symptom onsets. We also included another cohort of 215 samples as negative controls, 78 of which had positive serology test results of other infectious diseases or autoimmunity. Assay specificity was assessed by using a total of 847 anonymized samples which were collected before the Covid-19 pandemic from local patient populations seeking clinical care for rheumatoid diseases, thyroid cancer, and therapeutic drug monitoring.ResultsAbbott IgG, Euroimmun IgG/IgA had high precision, demonstrated by both intra- and inter-day CVs of <2%. There was no Abbott or Euroimmun IgG assay cross reactivity in the 78 samples with positive serology of non-SARS-CoV-2 infectious diseases and positive autoimmune antibodies. The Abbott IgG has specificity of 99.6%, while Euroimmun IgG and IgA were as high as 91.5% and 71.5%, respectively.ConclusionsOur evaluation confirmed high specificity of the Abbott IgG assay, while it was lower for Euroimmun IgG. Euroimmun IgA has suboptimal specificity which may limit its clinical use. Assay sensitivity was high for both Abbott and Euroimmun IgG assays.Copyright © 2020 Elsevier B.V. All rights reserved.

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