Multiple sclerosis diagnosis: free light chain testing as a possible valuable marker in cerebrospinal fluid

Background: the aim of the study was to assess the importance of free light-chain analysis in the Cerebrospinal Fluid (CSF) for the diagnosis of Multiple Sclerosis (MS) in patients visited at the General Hospital of Alessandria. Materials and Methods: detecting κFLC and λFLC levels in CSF and serum using Freelite tests on Optilite analyser (The Binding Site) and Isoelectric Focusing (IEF) on Hydrasis 2 analyser (Sebia). Statistical analysis was conducted by GraphPad statistical software and Excel statistical tools. Calculation of p-value by Kruskal-Wallis test and χ2 test. Evaluation of the Free Light Chain (FLC) indices’ performance through the construction of a Receiver Operating Characteristics (ROC) curve. Results: 132 CSF and serum samples were collected, and 25% of the patients were diagnosed with MS. Through the ROC analysis, the optimal cut-off value was found to be 6,56 for the K index, 10,12 for the λ index, and 0,65 for the IgG index. FLC indices were higher in MS patients than in others. Conclusions: the study shows that the K index has an equivalent reliability and a higher predictive value, but with lower costs and times than Oligoclonal Bands (OCB). The λ index could have the potential to become a further test used for differential diagnosis of MS, but more in-depth studies via more sensitive techniques are needed to evaluate real performance.