Rapid semi-quantitative point of care diagnostic test for post vaccination antibody monitoring

Introduction: Point-of-care (POC) quantification of the antibody responses against the 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 and compared to standard laboratory chemiluminescence (CLIA) based tests. Methods: Capillary- and venous blood samples were collected from 101 individuals employed at Copenhagen University Hospital, Denmark. Antibody responses were measured on capillary-, venous whole blood, plasma and diluted plasma samples directly on the POC instrument. POC results were available within seven minutes on the microfluidic cartridge reader. Plasma samples were analysed on the 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 data from the CLIA platform was used as a reference. Results: The Spearman rank 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 is found to be 0.86 and 0.90 respectively. ViroTrack Sero COVID-19 Total Ab furthermore showed high correlation (>0.86) among the different sample matrixes. The agreement for determination of samples >200 BAU/mL on POC and CLIA methods is estimated to be around 90%. Conclusion: ViroTrack Sero Covid Total Ab is a very rapid and simple-to-use POC test with high sensitivity and high correlation of the numerical results expressed in BAU/mL when compared to a commercial CLIA assay.