J Med Virol . Closing the Serological Gap in the Diagnostic Testing for COVID-19: The Value of Anti-SARS-CoV-2 IgA Antibodies

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J Med Virol


. 2020 Aug 13.
doi: 10.1002/jmv.26422. Online ahead of print.
Closing the Serological Gap in the Diagnostic Testing for COVID-19: The Value of Anti-SARS-CoV-2 IgA Antibodies


Maria Infantino ¹ , Mariangela Manfredi ¹ , Valentina Grossi ¹ , Barbara Lari ¹ , Sergio Fabbri ^{1 2} , Maurizio Benucci ³ , Alberto Fortini ⁴ , Arianna Damiani ⁵ , Emanuela Maria Mobilia ⁶ , Marta Panciroli ⁷ , Silvia Pancani ⁸ , Giampaola Pesce ^{6 7}



Affiliations

• PMID: 32790181
• DOI: 10.1002/jmv.26422

Abstract

Background: During COVID-19 pandemic, the early diagnosis of patients is a priority. Serological assays, in particular IgM and IgG anti-SARS-CoV-2, have today several applications but the interpretation of their results remain an open challenge. Given the emerging role of the IgA isotype in the COVID-19 diagnostics, we aimed to identify the SARS-CoV-2 IgA antibodies in a COVID-19 population seronegative for IgM.
Methods: A total of 30 patients hospitalized in San Giovanni di Dio Hospital (Florence, Italy) for COVID-19, seronegative for IgM antibodies, have been studied for anti-SARS-CoV-2 antibodies. They all had a positive oro/nasopharyngeal swab reverse transcription polymerase chain reaction result. Assays used were a chemiluminescent assay measuring SARS-CoV-2 specific IgM and IgG (S+N) and an ELISA, measuring specific IgG (S1) and IgA antibodies against SARS-CoV-2.
Results: Among the 30 patients, eight were positive for IgA, seven were positive for IgG (N+S) and two for IgG (S1), at first point (5-7 days from the onset of symptoms). The IgA antibodies mean values at the second (9-13 days) and third (21-25 days) time points were even more than twice as high as IgG assays. The agreement between the two IgG assays was moderate (Cohen's K = 0.59; SE = 0.13).
Conclusions: The inclusion of the IgA antibodies determination among serological tests of the COVID-19 diagnostic is recommended. IgA antibodies may help to close the serological gap of the COVID-19. Variations among anti-SARS-CoV-2 IgG assays should be considered in the interpretation of results. This article is protected by copyright. All rights reserved.

Keywords: Antiviral agents; Immune globulin; Immune responses; Immunoglobulin; SARS coronavirus; Virus classification.