Comparison of 16 Serological SARS-CoV-2 Immunoassays in 16 Clinical Laboratories

Harritshøj, Lene H.; Gybel-Brask, Mikkel; Afzal, Shoaib; Kamstrup, Pia R.; Jørgensen, Charlotte S.; Thomsen, Marianne Kragh; Hilsted, Linda; Friis-Hansen, Lennart; Szecsi, Pal B.; Pedersen, Lise; Nielsen, Lene; Hansen, Cecilie B.; Garred, Peter; Korsholm, Trine-Line; Mikkelsen, Susan; Nielsen, Kirstine O.; Møller, Bjarne K.; Hansen, Anne T.; Iversen, Kasper K.; Nielsen, Pernille B.; Hasselbalch, Rasmus B.; Fogh, Kamille; Norsk, Jakob B.; Kristensen, Jonas Henrik; Schønning, Kristian; Kirkby, Nikolai S.; Nielsen, Alex C. Y.; Landsy, Lone H.; Loftager, Mette; Holm, Dorte K.; Nilsson, Anna C.; Sækmose, Susanne G.; Grum-Schwensen, Birgitte; Aagaard, Bitten; Jensen, Thøger G.; Nielsen, Dorte M.; Ullum, Henrik; Dessau, Ram B.

Serological assays for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are needed to support clinical diagnosis and epidemiological investigations. Recently, assays for large-scale detection of total antibodies (Ab), immunoglobulin G (IgG), and IgM against SARS-CoV-2 antigens have been developed, but there are limited data on the diagnostic accuracy of these assays. This study was a Danish national collaboration and evaluated 15 commercial and one in-house anti-SARS-CoV-2 assays in 16 laboratories. Sensitivity was evaluated using 150 samples from individuals with asymptomatic, mild, or moderate COVID-19, nonhospitalized or hospitalized, confirmed by nucleic acid amplification tests (NAAT); samples were collected 13 to 73 days either from symptom onset or from positive NAAT (patients without symptoms). Specificity and cross-reactivity were evaluated in samples collected prior to the SARS-CoV-2 epidemic from >586 blood donors and patients with autoimmune diseases, cytomegalovirus or Epstein-Barr virus infections, and acute viral infections. A specificity of ≥99% was achieved by all total-Ab and IgG assays except one, DiaSorin Liaison XL IgG (97.2%). Sensitivities in descending order were Wantai ELISA total Ab (96.7%), CUH-NOVO in-house ELISA total Ab (96.0%), Ortho Vitros total Ab (95.3%), YHLO iFlash IgG (94.0%), Ortho Vitros IgG (93.3%), Siemens Atellica total Ab (93.2%), Roche Elecsys total Ab (92.7%), Abbott Architect IgG (90.0%), Abbott Alinity IgG (median 88.0%), DiaSorin Liaison XL IgG (median 84.6%), Siemens Vista total Ab (81.0%), Euroimmun/ELISA IgG (78.0%), and Snibe Maglumi IgG (median 78.0%). However, confidence intervals overlapped for several assays. The IgM results were variable, with the Wantai IgM ELISA showing the highest sensitivity (82.7%) and specificity (99%). The rate of seropositivity increased with time from symptom onset and symptom severity.