tetano
Editor, Senior Moderator
Eur J Clin Microbiol Infect Dis
. 2020 Nov 11.
doi: 10.1007/s10096-020-04104-2. Online ahead of print.
Evaluating the serological status of COVID-19 patients using an indirect immunofluorescent assay, France
S Edouard[SUP] 1 2 [/SUP], P Colson[SUP] 1 2 [/SUP], C Melenotte[SUP] 1 [/SUP], F Di Pinto[SUP] 1 [/SUP], L Thomas[SUP] 1 [/SUP], B La Scola[SUP] 1 2 [/SUP], M Million[SUP] 1 2 [/SUP], H Tissot-Dupont[SUP] 1 [/SUP], P Gautret[SUP] 1 3 [/SUP], A Stein[SUP] 1 2 [/SUP], P Brouqui[SUP] 1 2 [/SUP], P Parola[SUP] 1 3 [/SUP], J-C Lagier[SUP] 1 2 [/SUP], D Raoult[SUP] 1 2 [/SUP], Michel Drancourt[SUP] 4 5 [/SUP]
Affiliations
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 ≥ 1:200, 98.6% for IgM titre ≥ 1:200 and 96.3% for IgG titre ≥ 1:100 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.
. 2020 Nov 11.
doi: 10.1007/s10096-020-04104-2. Online ahead of print.
Evaluating the serological status of COVID-19 patients using an indirect immunofluorescent assay, France
S Edouard[SUP] 1 2 [/SUP], P Colson[SUP] 1 2 [/SUP], C Melenotte[SUP] 1 [/SUP], F Di Pinto[SUP] 1 [/SUP], L Thomas[SUP] 1 [/SUP], B La Scola[SUP] 1 2 [/SUP], M Million[SUP] 1 2 [/SUP], H Tissot-Dupont[SUP] 1 [/SUP], P Gautret[SUP] 1 3 [/SUP], A Stein[SUP] 1 2 [/SUP], P Brouqui[SUP] 1 2 [/SUP], P Parola[SUP] 1 3 [/SUP], J-C Lagier[SUP] 1 2 [/SUP], D Raoult[SUP] 1 2 [/SUP], Michel Drancourt[SUP] 4 5 [/SUP]
Affiliations
- PMID: 33179133
- DOI: 10.1007/s10096-020-04104-2
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 ≥ 1:200, 98.6% for IgM titre ≥ 1:200 and 96.3% for IgG titre ≥ 1:100 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.