Rapid Quantitative Point-Of-Care Diagnostic Test for Post COVID-19 Vaccination Antibody Monitoring

Abstract

Point-of-care (POC) quantification of antibody responses against SARS-CoV-2 spike protein can enable decentralized monitoring of immune responses after infection or vaccination. We evaluated a novel POC microfluidic cartridge-based device (ViroTrack Sero COVID-19 Total Ab) for quantitative detection of total antibodies against SARS-CoV-2 spike trimeric spike protein compared to standard laboratory chemiluminescence (CLIA)-based tests. Antibody responses of 101 individuals were measured on capillary blood, venous whole blood, plasma, and diluted plasma samples directly on the POC. Results were available within 7 min. As the reference, plasma samples were analyzed on DiaSorin LIAISON XL CLIA analyzer using LIAISON SARS-CoV-2 IgM, LIAISON SARS-CoV-2 S1/S2 IgG, and LIAISON SARS-CoV-2 TrimericS IgG assays. The Spearman rank's correlation coefficient between ViroTrack Sero COVID-19 Total Ab and LIAISON SARS-CoV-2 S1/S2 IgG and LIAISON SARS-CoV-2 TrimericS IgG assays was found to be 0.83 and 0.89, respectively. ViroTrack Sero COVID-19 Total Ab showed high correlation between the different matrixes. Agreement for determination of samples of >230 binding antibody units (BAU)/mL on POC and CLIA methods is estimated to be around 90%. ViroTrack Sero Covid Total Ab is a rapid and simple-to-use POC test with high sensitivity and correlation of numerical results expressed in BAU/mL compared to those of a commercial CLIA assay. IMPORTANCE Serological testing is an important diagnostic support tool in the fight against COVID-19. So far, serological testing has been performed on either lateral flow assays, which perform only qualitatively and can be difficult for the individual to read, or standard laboratory assays, which are time- and resource-consuming. The purpose of the study was to evaluate the performance of a new POC microfluidic cartridge-based device based on immunomagnetic agglutination assay that can provide an accurate numerical quantification of the total antibodies within only 7 min from a single drop of capillary blood. We demonstrated a high level of correlation between the POC and the two CLIA laboratory-based immunoassays from Diasorin, thus allowing a potentially wider use of quantitative serology tests in the COVID-19 pandemic.

Keywords: S protein trimer; SARS-CoV-2; immunomagnetic agglutination assay; point-of-care; rapid IgG-IgM-IgA combined test; vaccination.

FIG 1

LIAISON SARS-CoV-2 Trimeric IgG (A), S1/S2 IgG (B), and IgM (C) versus ViroTrack Sero COVID-19 Total Ab. For ViroTrack Sero COVID-19 Total Ab, results are shown for diluted plasma (orange points) at >230 BAU/mL; otherwise, undiluted results are shown (blue points). Results inside the dynamic range for Diasorin (<2,080 BAU/mL for Trimeric IgG and <400 AU/mL for S1/S2 IgG) and below 2,000 BAU/mL obtained for ViroTrack are shown.

FIG 2

Specimen type agreement between ViroTrack Sero COVID-19 Total Ab results, using capillary blood, venous blood, and plasma samples. (A) Undiluted capillary blood versus undiluted plasma samples. (B) Undiluted venous blood versus undiluted plasma samples.

FIG 3

Swam plot of plasma and diluted plasma measured with ViroTrack Sero COVID-19 Total Ab. Data divided into previous PCR confirmed infected (Infection) and previous noninfected (No infection). The dotted line shows 230 BAU/mL.