Evaluation of CSF kappa free light chains for the diagnosis of multiple sclerosis (MS): A comparison with oligoclonal bands (OCB) detection via isoelectric focusing (IEF) coupled with immunoblotting

This study was done to evaluate the diagnostic accuracy of cerebrospinal fluid kappa free light chain (KFLC) for diagnosis of multiple sclerosis, against isoelectrofocusing (IEF) to detect oligoclonal bands (OCB) as gold standard. 64 cases were divided into positive and negative based on the OCB results. Diagnostic accuracy was calculated for the 1 mg/L cut-off. The 1 mg/L cut-off yielded a percent agreement of 86.1% and Cohen's kappa value of 0.8. Youden's index, yielded a cut-off of 0.92 mg/L as optimal (90.3% specificity and 90.9% sensitivity). The analytical time was 3 hours and 55 min for IEF and 25 min for KFLC. The cost of a single OCB test was PKR12 000 (US$68.17) compared with PKR4150 (US$23.58) for KFLC. KFLC proved to be an accurate, cheaper and time-saving alternative and can be performed prior to the contemporary testing.