Clinical Use of κ Free Light Chains Index as a Screening Test for Multiple Sclerosis

Abstract

Abstract Objective To assess the usefulness of the κ free light chain index (κFLCi) as a screening test to identify patients with suspected MS. Methods The study included 56 patients with a request to test for oligoclonal bands (OCBs). OCBs were detected by isoelectric focusing, followed by immunofixation. Cerebrospinal fluid (CSF) and serum κFLC were measured by a turbidimetric assay. Also, the κFLC index (κFLCi) was calculated. Results CSF κFLC levels and κFLCi were significantly higher in patients with multiple sclerosis (MS) than in patients with other neurological diseases (NDs; P < .001 and P < .001, respectively). At the cutoff value of 2.9, the κFLCi detected MS with sensitivity of 97% and specificity of 65%. Overall, 92% patients with κFLCi of 2.9 or greater and who had tested positive for OCBs were diagnosed as having MS. Conclusion Our findings support the use of κFLCi as a screening test when MS is suspected, followed by OCB detection as a confirmatory test for the diagnosis of MS.