In MS diagnosis, the case for κ-FLC index
March 2026—An international panel of experts recommended including the determination of intrathecal kappa free light chain (κ-FLC) synthesis in the next revision of MS diagnostic criteria. The κ-FLC index, easily determined by nephelometry and turbidimetry, is a fast, cost-effective, and quantitative biomarker with high diagnostic value for MS. It also predicts future inflammatory disease activity and disability progression, making it a valuable prognostic tool.