Que Lam¹, Nicole Jenkins^1
1Alfred Pathology

Introduction:

The 2024 revised McDonald criteria for Multiple Sclerosis (MS) is anticipated to include CSF Kappa Free Light Change (KFLC) analysis as an indicator of intrathecal immunoglobulin production, to be used alternatively to Oligoclonal Bands (OCB) for diagnosis. We compared three proposed CSF KFLC parameters to our long-established OCB test by isoelectric focusing (IEF) and immune-detection.

45 CSF/serum paired samples for OCB testing were also analysed for KFLC and albumin by immunoturbidimetry on the Optilite (Binding Site, UK).  14/45 demonstrated intrathecal production of OCB by IEF. 31/45 were negative including 12 showing systemic production. CSF KFLC parameters were calculated as per the 2023 consensus statement¹ and assessed using literature-derived cut-offs. Performance against IEF (sensitivity, specificity) was determined for KFLC concentration (79%, 90%); Kappa Index (100%, 97%); Intrathecal Fraction KFLC (IF-KFLC) using Quotient Albumin-dependent upper normal limit as described by Presslauer et al. (100%, 97%), Hegen et al. (100%, 100%), Senel et al. (71%, 100%) and Reiber et al. (71%, 100%).

Our findings support the use of CSF KFLC analysis, particularly Kappa Index, as an alternative to OCB by IEF. However, the robustness of the fixed cut-off should be monitored with changing assay production lots. 

1.      Hegen et al. Cerebrospinal fluid kappa free light chains for the diagnosis of multiple sclerosis: A consensus statement. Multiple Sclerosis Journal 2023, Vol. 29(2) 182–195

All authors have contributed to the design of the study and the analysis and interpretation of the data. NJ and VD were also involved in conducting the testing (IEF and Immunoturbidimetric assays). AI was not used in the writing process for this abstract.