Antibody and antigen testing
Serum IgG antibodies against S1 and NCP antigens of SARS-CoV-2 were
measured by commercial ELISAs (Anti-SARS-CoV-2-ELISA [IgG] and
Anti-SARS-CoV-2-NCP-ELISA [IgG]; Euroimmun, Lübeck, Germany),
according to the manufacturer’s instructions. Upon manual dilution, sera
were processed in a BEPIII analyzer (Siemens, Eschborn, Germany).
Results are indicated as Ratio (cutoff: <0.8; borderline:
≥0.8, <1.1; positive: >1.1). Circulating NCP
antigen in serum was quantified using the ScheBo®
SARS-CoV-2TM Antigen ELISA (ScheBo Biotech, Gießen,
Germany). Values ≥2.97 pg/mL were considered positive.