Performance evaluation of novel fluorescent-based lateral immune flow assay (LIFA) for rapid detection and quantification of total anti-SARS-CoV-2 S-RBD binding antibodies in infected individuals.

Overview

BACKGROUND: The vast majority of the commercially available LFIA is used to detect SARS-CoV-2 antibodies qualitatively. Recently, a novel fluorescence-based LIFA test was developed for quantitative measurement of the total binding antibody units (BAU/mL) against the receptor-binding domain of the SARS-CoV-2 spike protein (S-RBD). AIM: To evaluate the performance of the fluorescence LIFA Finecare^TM 2019-nCoV S-RBD test along with its reader (Model No.: FS-113). METHODS: Plasma from 150 RT-PCR confirmed-positive individuals and 100 pre-pandemic samples were tested by FinCare^Tm to access sensitivity and specificity. For qualitative and quantitative validation of the FinCar^Tm measurements, the BAU/mL results of FinCare^Tm were compared with results of two reference assays: the surrogate virus-neutralizing test (sVNT, GenScript, USA), and the VIDAS®3 automated assay (BioMérieux, France). RESULTS: Finecare^TM showed 92% sensitivity and 100% specificity compared to PCR. Cohen's Kappa statistic denoted moderate and excellent agreement with sVNT and VIDAS®3, ranging from 0.557 (95% CI: 0.32-0.78) to 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 post-infection or vaccination, particularly in none or small laboratory settings.