Free light chains as a reliable biomarker of intrathecal synthesis in the diagnosis of CNS inflammatory diseases

To address the diagnostic performances of cerebrospinal fluid (CSF) free light chains (FLC) measurements compared to oligoclonal bands (OCB) to support multiple sclerosis (MS) diagnosis. kFLC index showed the highest diagnostic accuracy to detect MS patients with the highest AUC compared to OCB, IgG index, IF kFLC R, kFLC H, λFLC index and IF λFLC. FLC indices are biomarkers of intrathecal Immunoglobulin synthesis and central nervous system (CNS) inflammation. kFLC index can discriminate between MS and other CNS inflammatory disorders, while λFLC index is less informative for MS but can play a role to support the diagnosis of other inflammatory CNS disorders. [Display omitted] •CSF Oligoclonal bands analysis is qualitative and has several limitations.•CSF FLC indices are diagnostic biomarkers of immunoglobulin intrathecal synthesis.•kFLC index has higher sensitivity and NPV but lower specificity than OCB in MS.•λFLC can support the diagnosis of inflammatory diseases other than MS.•IF do not add significant diagnostic value in respect with the kFLC index.