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(TM) 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(TM) to access sensitivity and specificity. For qualitative and quantitative validation of the FinCare(TM) measurements, BAU/mL results of FinCare(TM) 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(TM) 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(TM)/sVNT (r = 0.7, p < 0.0001) and Finecare(TM)/VIDAS®3 (r = 0.8, p < 0.0001). CONCLUSION: Finecare(TM) 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.