Evaluating the serological status of COVID-19 patients using an indirect immunofluorescent assay, France.
Eur J Clin Microbiol Infect Dis
; 40(2): 361-371, 2021 Feb.
Article
in English
| MEDLINE | ID: covidwho-920023
ABSTRACT
An indirect in-house immunofluorescent assay was developed in order to assess the serological status of COVID-19 patients in Marseille, France. Performance of IFA was compared to a commercial ELISA IgG kit. We tested 888 RT-qPCR-confirmed COVID-19 patients (1302 serum samples) and 350 controls including 200 sera collected before the pandemic, 64 sera known to be associated with nonspecific serological interference, 36 sera from non-coronavirus pneumonia and 50 sera from patient with other common coronavirus to elicit false-positive serology. Incorporating an inactivated clinical SARS-CoV-2 isolate as the antigen, the specificity of the assay was measured as 100% for IgA titre ≥ 1200, 98.6% for IgM titre ≥ 1200 and 96.3% for IgG titre ≥ 1100 after testing a series of negative controls. IFA presented substantial agreement (86%) with ELISA EUROIMMUN SARS-CoV-2 IgG kit (Cohen's Kappa = 0.61). The presence of antibodies was then measured at 3% before a 5-day evolution up to 47% after more than 15 days of evolution. We observed that the rates of seropositivity as well as the titre of specific antibodies were both significantly higher in patients with a poor clinical outcome than in patients with a favourable evolution. These data, which have to be integrated into the ongoing understanding of the immunological phase of the infection, suggest that detection anti-SARS-CoV-2 antibodies is useful as a marker associated with COVID-19 severity. The IFA assay reported here is useful for monitoring SARS-CoV-2 exposure at the individual and population levels.
Full text:
Available
Collection:
International databases
Database:
MEDLINE
Main subject:
Fluorescent Antibody Technique, Indirect
/
SARS-CoV-2
/
COVID-19
/
Antibodies, Viral
Type of study:
Diagnostic study
/
Experimental Studies
/
Prognostic study
Limits:
Adolescent
/
Adult
/
Aged
/
Female
/
Humans
/
Male
/
Middle aged
/
Young adult
Language:
English
Journal:
Eur J Clin Microbiol Infect Dis
Journal subject:
Communicable Diseases
/
Microbiology
Year:
2021
Document Type:
Article
Affiliation country:
S10096-020-04104-2
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