Diagnostic Value of the Kappa Free Light Chain Index to Distinguish MOGAD, NMOSD, and MS

The differential diagnosis between aquaporin-4-immunoglobulin G–positive neuromyelitis optica spectrum disorder (AQP4-NMOSD), myelin oligodendrocyte glycoprotein (MOG) antibody–associated disease (MOGAD), and multiple sclerosis (MS) can be complex. Kappa free light chain index (KFLC-Index) emerged as an effective biomarker for distinguishing patients with MS from patients with other conditions. The main aim of this study was to assess the diagnostic performance of KFLC-Index in differentiating MOGAD, AQP4-NMOSD, and MS and to compare it with CSF-restricted oligoclonal bands (OCB) performance.