Detection of SARS-CoV-2-specific Antibodies via Rapid Diagnostic Immunoassays in COVID-19 Patients with Positive SARS-CoV-2 RNA Real-time Reverse Transcriptase PCR Results

Abstract

Background: Efficient monitoring and control of coronavirus disease 2019 (COVID-19) requires access to diagnostic tests, and serological diagnostic testing is desirable. In the current study antibodies were investigated in patients recently diagnosed with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection.Methods: Cross-sectional data derived from 245 patients in whom SARS-CoV-2 infection had been confirmed via real-time reverse transcriptase-polymerase chain reaction were obtained. Samples were acquired at the onset of COVID-19 symptoms or the first detection of SARS-CoV-2 in asymptomatic patients, and at another timepoint within 8 weeks thereafter. All specimens were tested simultaneously using an IgM/IgG rapid diagnostic test (RDT), nucleocapsid-based and spike protein-based IgG immunoassays, and a spike protein‑based IgA immunoassay. Blood donor samples obtained in 2018 were used as negative controls, and to assess cross-reactivity with seasonal coronaviruses. Results: The IgM/IgG RDT exhibited 97.5% sensitivity and 97.2% specificity compared with a nucleocapsid-IgG-based chemiluminescent microparticle immunoassay, and 98.4% sensitivity and 93.6% specificity compared with a spike protein-based ELISA. IgG RDT detection was 100% concordant with IgG and IgA immunoassays (P < 0.001). IgM, IgG, and IgA were low during the first week after COVID-19 symptom onset or the detection of SARS-CoV-2 RNA. IgM began decreasing after 4 weeks, whereas IgG and IgA remained at appreciable levels over the 8-week study period. No cross-reactivity with seasonal coronaviruses was detected.Conclusions: IgM/IgG RDTs alone or combined with molecular diagnostic tests may be useful for identifying recent SARS-CoV-2 infection.