Performance evaluation of Abbott ARCHITECT SARS-CoV-2 IgG immunoassay in comparison with indirect immunofluorescence and virus microneutralization test

Highlights • Performance of Abbott ARCHITECT SARS-CoV-2 IgG assay was retrospectively evaluated. • The assay showed a very high specificity compared to IFA. • Sensitivity was 100% for samples collected after 14 days post-symptoms onset. • Sensitivity vs. microneutralization was 94.4%.
Background Serological tests for anti-SARS-CoV-2 antibodies are becoming of great interest to determine seroprevalence in a given population, define previous exposure and identify highly reactive human donors for the generation of convalescent serum as therapeutic. Objectives We evaluated the diagnostic performance of the Abbott ARCHITECT SARS-CoV-2 IgG test, a fully automated indirect immunoassay that detects antibodies directed to a recombinant SARS-CoV-2 Nucleocapsid antigen. Study design Abbott ARCHITECT SARS-CoV-2 IgG immunoassay was compared to an indirect immunofluorescence assay (IFA) on sera from patients with COVID-19 collected at different days after symptoms onset or infected by other human coronaviruses. Comparison with neutralization test was also performed. Results After 7, 14 and >14 days after onset ARCHITECT was positive on 8.3%; 61.9% and 100% of the tested samples compared to 58.3%; 85.7% and 100% by IFA. The sensitivity was 72% vs. IFA and 66.7% vs. a real-time PCR, the specificity was 100%. On 18 samples with neutralizing activity, 17 were positive by Abbott ARCHITECT SARS-CoV-2 IgG. Conclusions In our study, Abbott ARCHITECT SARS-CoV-2 IgG assay showed a satisfactory performance, with a very high specificity. IgG reactivity against SARSCoV-2 N antigen was detectable in all patients by two weeks after symptoms onset. In addition, concordance between this serological response and viral neutralization suggests that a strong humoral response may be predictive of a neutralization activity, regardless of the target antigens. This finding supports the use of this automated serological assay in diagnostic algorithm and public health intervention, especially for high loads of testing.