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

Link to article at PubMed

J Med Virol. 2020 Aug 13. doi: 10.1002/jmv.26422. Online ahead of print.


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.

PMID:32790181 | DOI:10.1002/jmv.26422

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