SARS-CoV-2 antibody tests
Specific antibody response to SARS-CoV-2 was evaluated by the use of two
different test kits: the commercially available, licensed qualitative
Elecsys Anti-SARS-CoV-2 (Roche Diagnostics, Rotkreuz, Switzerland;
https://diagnostics.roche.com)
and a validated and published in-house ELISA.12 The
Elecsys Anti-SARS-CoV-2 assay does not discriminate between the antibody
type(s) present and can detect IgA, IgM, and IgG. The test is based on a
recombinant nucleocapsid (N) antigen and has a cutoff value of 1.0
(S/Co). The in-house ELISA is based on SARS-CoV-2 S-protein’s
receptor-binding domain, quantifies total IgG and has a cutoff value of
1.0 (S/Co). The detected reactivity correlates with the SARS-CoV-2
neutralization titer as described previously.12 All
samples with S/Co <1.0 were considered negative. In this
experimental setting, strong antibody responses of S/Co ≥100 in the
Elecsys Anti-SARS-CoV-2 test were considered for clinical follow-up for
PMIS.