Performance of Elecsys anti-SARS CoV-2 (Roche) and VIDAS anti-SARS CoV-2 (biomérieux) for SARS-CoV-2 nucleocapsid and spike protein antibody detection

Abstract

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the novel viral pathogen that causes coronavirus disease 2019 (COVID-19) in humans, has spread worldwide since its identification in late 2019. The pandemic produced an accelerated development of new serological techniques for diagnosis.

Herein, we evaluated two commercial assays for serological diagnosis of SARS-CoV-2 infection: Elecsys Anti-SARS CoV-2 (Roche), for nucleocapsid total antibody detection and VIDAS Anti- SARS CoV-2 (bioMérieux), for spike protein IgG antibody detection.

The Elecsys Anti-SARS CoV-2 assay was performed on a Cobas e411 analyzer (Roche Diagnostics) and conducted according to the manufacturer’s instructions. Results are expressed as (cut-off index, negative COI <1 or positive COI ≥1) for anti-SARS CoV-2 total antibodies. The VIDAS SARS-CoV-2 IgG assay was performed on a VIDAS analyzer (bioMérieux) and conducted according to the manufacturer’s instructions. Results are interpreted as negative (index <1) or positive (index ≥1). Sensitivity was assessed using a panel of 92 plasma samples from recovered COVID-19 patients who were positive for RT-PCR and positive for neutralizing antibodies by PRNT and/or positive for IgG antibodies by indirect immunofluorescence assay (IFA). Specificity was determined studying 71 plasma samples collected during year 2018, prior to the COVID-19 pandemic. Categorical variables were compared using Fisher’s exact test (CI 95%). Additionally, concordance between the two commercial assays was analyzed using Cohen's kappa coefficient (κ).

Sensitivity: 97.83% and 98.91% for Roche and bioMérieux assays, respectively, specificity: 98.59% (Roche) and 97.18% (bioMérieux), positive predictive value (PPV): 98.90% (Roche) and 97.85% (bioMérieux), and negative predictive value: (NPV) 97.22% (Roche) and 98.57% (bioMérieux). Additionally, Cohen's kappa coefficient demonstrated high concordance (k=0.950) between Elecsys Anti-SARS CoV-2 and VIDAS Anti-SARS CoV-2.

In conclusion, these results evidenced a very good performance for both, the nucleocapsid antibody assay (Elecsys Anti-SARS CoV-2; Roche) and the spike protein antibody assay (VIDAS Anti-SARS CoV-2; bioMérieux), being both platforms equally adequate for indirect diagnosis of SARS-CoV-2 infection through total antibodies and IgG antibody detection, respectively.