Live Cell-Based Flow Cytometry Assay Versus Commercial Cell-Based Indirect Immunofluorescence Assay of Aquaporin-4 Antibody in Neuromyelitis Optica: A Comparative Study.

INTRODUCTION

Neuromyelitis Optica (NMO) is an inflammatory disorder affecting the central nervous system, notably the optic nerve and spinal cord. Seropositive NMO is marked by serum IgG antibodies against aquaporin-4 (AQP4). The accurate identification of AQP4-IgG is crucial for distinguishing NMO from other demyelinating diseases of the central nervous system. However, traditional diagnostic assays have limitations in sensitivity and specificity. Here, we introduce our in-house flow cytometry live cell-based assay (FC-LCBA) for detecting AQP4 antibodies with enhanced sensitivity and specificity. Our objective is to report the accuracy and compare the efficacy of our newly developed in-house FC-LCBA against the commercial cell-based indirect immunofluorescence assay (IIFA) in detecting AQP4 antibodies.

METHODS

This single-blind study was approved by the ethical committee and involved 101 serum samples. Twenty-five samples (including retests) from 17 patients evaluated in the NMO spectrum who had at least one positive cell-based IIFA test during the diagnosis or follow-up are tested in parallel with our in-house FC-LCBA and cell-based IIFA. In addition, 36 serum samples from myelin oligodendrocyte glycoprotein-associated disease (MOGAD) patients and 40 serum samples from healthy subjects are also referred for specificity analysis.

RESULTS

Our in-house FC-LCBA displayed superior sensitivity, detecting positive results even when the cell-based IIFA yielded negative results in patients under immunosuppressive treatments. Additionally, FC-LCBA exhibited high specificity for NMO, showing negligible antibody levels in patients with MOGAD diagnosis and healthy individuals. The assay's stability was confirmed through consistent results in retests.

CONCLUSION

Our in-house FC-LCBA emerges as a promising diagnostic tool for detecting AQP4 antibodies, offering improved sensitivity, specificity, and reliability, instilling confidence in its potential.