Evaluation of ELISA tests for the qualitative determination of IgG, IgM and IgA to SARS-CoV-2

Francesca Colavita, Alessandra Brogi, Daniele Lapa, Licia Bordi, Giulia Matusali, Silvia Meschi, Patrizia Marsella, Giulia Tesi, Tommaso Bandini, Antonino Di Caro, Maria Rosaria Capobianchi, Concetta Castilletti
doi: https://doi.org/10.1101/2020.05.24.20111682
This article is a preprint and has not been peer-reviewed [what does this mean?]. It reports new medical research that has yet to be evaluated and so should not be used to guide clinical practice.

Serological assays for anti-SARS-CoV-2 antibodies are now of critical importance to support diagnosis, guide epidemiological intervention, and understand immune response to natural infection and vaccine administration. We developed and validated new anti-SARS-CoV-2 IgG, IgM and IgA ELISA tests (ENZY-WELL SARS-CoV-2 ELISA, DIESSE Diagnostica Senese S.p.a.) based on whole-virus antigens. We used a total of 553 serum samples including samples from COVID-19 suspected and confirmed cases, healthy donors, and patients positive for other infections or autoimmune conditions. Overall, the assays showed good concordance with the indirect immunofluorescence reference test in terms of sensitivity and specificity. Especially for IgG and IgA, we observed high sensitivity (92.5 and 93.6%, respectively); specificity was high (>96%) for all antibody types ELISAs. In addition, sensitivity was linked to the days from symptoms onset (DSO) due to the seroconversion window, and for ENZY-WELL SARS-CoV-2 IgG and IgA ELISAs resulted 100% in those samples collected after 10 and 12 DSO, respectively. The results showed that ENZY-WELL SARS-CoV-2 ELISAs may represent a valid option for both diagnostic and epidemiological purposes, covering all different antibody types developed in SARS-CoV-2 immune response.

Competing Interest Statement
Alessandra Brogi, Giulia Tesi and Tommaso Bandini are employees of the DIESSE Diagnostica Senese S.p.a. (Siena, Italy). In no way their contribution to the completion of the study influenced the study design and the analysis of the results. No additional conflict of interest or other competing relationships exist.

Funding Statement
This research was carried out in the framework of a scientific collaboration between INMI and DIESSE Diagnostica Senese S.p.a. and supported by Ministry of Health (Ricerca Corrente and Conto Capitale 2017), and European Commission Horizon 2020 (European Virus Archive GLOBAL, 871029; EU project 101003544, CoNVat; EU project 101003551, EXSCALATE4CoV).

Author Declarations
I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.


The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

The study was approved from the INMI Ethical Board. Informed consent was not required as human samples used for this work were residual samples from routine diagnostic activities, patients' data remained anonymous, and the results obtained with the new tests were not used for the clinical management of the patient.

All necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived.


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Paper in collection COVID-19 SARS-CoV-2 preprints from medRxiv and bioRxiv