INTRODUCTION: The development of SARS-CoV-2 serological tests is massive. The external validation of their performance is needed before use in clinical routine practice.
OBJECTIVES: Our study aims at assessing the analytical and clinical performance of 2 ELISA tests detecting antibodies directed against the virus nucleocapsid protein: The NovaLisa® SARS-CoV-2 IgG, IgA, and IgM test (NovaTec®) allowing a separate detection of each antibody and the Platelia® SARS-CoV-2 Total Ab test (Bio-Rad®) detecting total antibodies (IgM, IgA and IgG).
METHODS: Two hundred and eight COVID-19 samples from 48 RT-qPCR confirmed patients were used to perform the sensitivity analysis. Non-SARS-CoV-2 sera (n = 79) with a potential cross-reaction to SARS-CoV-2 immunoassays were included in the specificity analysis. In addition, using ROC curves, adapted cut-off for improvement of the performances were proposed. The kinetics of these antibodies was also assessed over 8 weeks.
RESULTS: Two weeks after the RT-qPCR positive detection, the NovaLisa® test shows a sensitivity and specificity of 94.9% (95%CI: 83.1-98.6%) and 96.2% (95%CI: 89.4-98.7%) for IgG, of 89.7% (95%CI: 76.4-95.9%) and 98.7% (95%CI:93.2-98.8%) for IgA, and of 48.7% (95%CI: 33.9-63.8%) and 98.7% (95%CI:93.2-99.8%) for IgM. With the Platelia® system, the specificity and sensitivity were 97.4% (95%CI: 92.1-99.7%) and 94.9% (95%CI:87.7-98.0%) for total antibodies using the adapted cut-offs.
CONCLUSION: The NovaLisa® and the Platelia® tests have satisfactory analytical performances. The clinical performances are excellent for IgG, IgA and total antibodies especially if the cut-off is optimized. This article is protected by copyright. All rights reserved.