Abstract
Currently available COVID-19 antibody tests using enzyme immunoassay (EIA) or immunochromatographic assay have variable sensitivity and specificity. Here, we developed and evaluated a novel microsphere-based antibody assay (MBA) for detecting immunoglobulin G (IgG) against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleoprotein (NP) and spike protein receptor binding domain (RBD). The seropositive cutoff value was set using a cohort of 294 anonymous serum specimens collected in 2018. The specificity was assessed using serum specimens collected from organ donors or influenza patients before 2020. Seropositive rate was determined among COVID-19 patients. Time-to-seropositivity and signal-to-cutoff (S/CO) ratio were compared between MBA and EIA. MBA had a specificity of 100% (93/93; 95% confidence interval (CI), 96–100%) for anti-NP IgG, 98.9% (92/93; 95% CI 94.2–100%) for anti-RBD IgG. The MBA seropositive rate for convalescent COVID-19 patients was 89.8% (35/39) for anti-NP IgG and 79.5% (31/39) for anti-RBD IgG. The time-to-seropositivity was shorter with MBA than EIA. MBA could better differentiate between COVID-19 patients and negative controls with higher S/CO ratio for COVID-19 patients, lower S/CO ratio with negative controls and fewer specimens in the equivocal range. MBA is robust, simple and is suitable for clinical microbiology laboratory for the accurate determination of anti-SARS-CoV-2 antibodies for diagnosis, serosurveillance, and vaccine trials.
Highlights
In 2003, severe acute respiratory syndrome coronavirus (SARS-CoV) caused the first severe coronavirus epidemic, leading to more than 8000 cases, mainly in Asia [1,2]
Lateral flow immunochromatographic assay allows for rapid detection, but currently available antibody testing assays for SARS-CoV-2 mainly rely on enzyme immunoassay or lateral flow immunochromatographic assays and the sensitivities of these assays are relatively low [10]
We developed and evaluated an in-house microsphere-based antibody assay (MBA) for the detection of immunoglobulin G (IgG) against SARS-CoV-2 nucleoprotein (NP) and spike protein receptor binding domain (RBD)
Summary
In 2003, severe acute respiratory syndrome coronavirus (SARS-CoV) caused the first severe coronavirus epidemic, leading to more than 8000 cases, mainly in Asia [1,2]. Antibody testing allows the retrospective diagnosis of an infection by comparing the antibody titer at the acute and at the convalescent phase of the illness. This is especially important for patients whose viral load is too low to be detected by virus detection assays. Enzyme immunoassay is a commonly used antibody assay for the detection of SARS-CoV-2 [5,7,8]. Lateral flow immunochromatographic assay allows for rapid detection, but currently available antibody testing assays for SARS-CoV-2 mainly rely on enzyme immunoassay or lateral flow immunochromatographic assays and the sensitivities of these assays are relatively low [10]
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call