Performance Evaluation of Novel Fluorescent-based Lateral Flow Immunoassay (LFIA) for Rapid Detection and Quantification of Total Anti-SARS-CoV-2 S-RBD Binding Antibodies in Infected Individuals

Background: A vast majority of the commercially available lateral flow immunoassay (LFIA) is used to detect SARS-CoV-2 antibodies qualitatively. Recently, a novel fluorescence-based lateral flow immunoassay (LFIA) test was developed for quantitative measurement of the total binding antibody units (BAUs) (BAU/mL) against SARS-CoV-2 spike protein receptor-binding domain (S-RBD).

Aim: This study aimed to evaluate the performance of the fluorescence LFIA Finecare 2019-nCoV S-RBD test along with its reader (Model No.: FS-113).

Methods: Plasma from 150 reverse trancriptase-PCR (RT-PCR)-confirmed positive individuals and 100 prepandemic samples were tested by Fincare to access sensitivity and specificity. For qualitative and quantitative validation of the FinCare measurements, BAU/mL results of FinCare were compared with results of 2 reference assays: the surrogate virus-neutralizing test (sVNT, GenScript Biotech, USA) and the VIDAS®3 automated assay (BioMérieux, France).

Results: Finecare showed 92% sensitivity and 100% specificity compared with PCR. Cohen's Kappa statistic denoted moderate and excellent agreement with sVNT and VIDAS®3, with values being 0.557 (95% CI: 0.32-0.78) and 0.731 (95% CI: 0.51-0.95), respectively. A strong correlation was observed between Finecare/sVNT (r = 0.7, p < 0.0001) and Finecare/VIDAS®3 (r = 0.8, p < 0.0001).

Conclusion: Finecare is a reliable assay and can be used as a surrogate to assess binding and neutralizing antibody response after infection or vaccination, particularly in none or small laboratory settings.