Kappa index and oligoclonal bands detection in cerebrospinal fluid samples of patients with suspected multiple sclerosis

Abstract

Introduction: The evaluation of the intrathecal production of immunoglobulin G (IgG) can be useful in the evaluation of multiple sclerosis (MS) suspected cases and the most important test to verify it is the detection of oligoclonal bands (OCBs) in cerebrospinal fluid (CSF) and serum. Recent studies have reported that measuring CSF IgG free light chains (FLC), especially the Kappa Index, is comparable with OCBs as markers of IgG synthesis. It is still unknown if diagnostic sensitivity be increased by performing these two methods in parallel. Objectives: The aim of this study was to evaluate the results of the Kappa index and the oligoclonal bands (BOCs) in samples from patients with suspected MS. Methods: Patients with suspected MS underwent CSF analysis. Intrathecal synthesis of IgG was evaluated with BOCs, IgG index, Reiber nomogram, and kappa index. Results: One hundred and seventy-one serum and CSF samples were included, 76 of them had positive CSF BOC. Among the BOC+ cases, 48 (63.2%) were also positive with the Reiber nomogram, 53 (69.7%) were also positive with the IgG index, and 74 (97.4%) were also positive with the kappa index. Among the patients without BOCs, 5 (5.2%) cases had a positive Reiber, eight had a positive IgG index (8.4%), and eight (8.4%) had a positive kappa index. Conclusion: The Kappa index was the method with the highest association with BOCs, confirming that this method is at least as sensitive as the detection of BOCs. Positive kappa results found among cases without BOCs may be false positives but may also indicate false negative results with BOC. Therefore, it is possible that kappa index can help to diagnose cases of MS without detection of BOCs.