Elecsys anti sars cov 2 assay

Between May 11, 2020, and July 2, 2020, 109 patients diagnosed with COVID‐19 disease 10 weeks previously (71.2 ± 16.5 days) were enrolled into this study. The 109 patients had rtPCR‐confirmed (n = 92, 84.4%) and/or SARS‐CoV‐2 antibody‐confirmed (Elecsys^® Anti‐SARS‐CoV‐2 assay Roche) (n = 108 tested, n = 107 positive, 99.1%) COVID‐19 disease.³⁴ In parallel, 98 healthy control subjects, who were reportedly asymptomatic for the last 10 weeks and who were SARS‐CoV‐2 negative by certified SARS‐CoV‐2 antibody test (Elecsys^® Anti‐SARS‐CoV‐2 assay Roche) and had a negative rtPCR test for SARS‐CoV‐2 at the time of venipuncture, were enrolled into the study. Similar to the COVID‐19‐infected patients also the HC collective had different co‐morbidities as specified in Table 1. All patients gave their written informed consent in accordance with the Declaration of Helsinki. The study was approved by the Ethics Committee of the Medical University of Vienna (EK No.: 1302/2020). Venous blood was drawn from all subjects and was either EDTA‐anticoagulated (for flow cytometric analyses and determination of lymphocyte emigration rates from thymus using TREC and bone marrow using KREC technology), heparin‐anticoagulated (for cryopreservation of PBMC), or silicon dioxide coagulated (to obtain serum for determining specific antibodies).

All serological tests were performed using both the Abbott ARCHITECT SARS-CoV-2 IgG Assay (Abbott Laboratories, Abbott Park, IL, USA), an automated two-step immunoassay using SARS-CoV-2 antigen-coated paramagnetic microparticles, and the Roche Elecsys^® Anti-SARS-CoV-2 Assay (Roche Diagnostics GmbH – Mannheim, Germany), an electro-chemiluminescence immunoassay that quantifies total SARS-CoV-2-specific immunoglobulin (19 (link)). The Abbott ARCHITECT SARS-CoV-2 IgG Assay specifically measures anti-SARS-CoV-2 IgG antibodies whereas the Roche Elecsys^® Anti-SARS-CoV-2 Assay measures total anti-SARS-CoV-2 antibody, resulting in ~35-fold higher antibody titers in the Roche assay.

Antibodies against the SARS-CoV-2 spike (S1) protein receptor-binding domain (S1-AB) encompassing all immunoglobulin classes (panIg) were determined using chemiluminescent immunoassay (ECLIA) (Elecsys Anti-SARS-CoV-2 S, Roche Diagnostics GmbH, Mannheim, Germany) on a COBAS 8000 analyzer (Roche, Basel, Switzerland) as prescribed by the manufacturer. Samples were measured at 10-fold dilution (Roche Cobas Universal Diluent) and re-measured at 400-fold dilution when exceeding the upper detection limit (250 U/mL). Results ≥0.80 U/mL are considered positive. PanIg antibodies against the SARS-CoV-2 nucleocapsid antigen (N-AB) were similarly determined with ECLIA (Elecsys Anti-SARS-CoV-2 assay, Roche, Basel, Switzerland) using a cut-off index based on positive and negative calibrators normalized to WHO standards [10 ]. Results presenting a ratio of signal/cut-off ≥1.0 are considered positive.