Author Of 1 Presentation
P0267 - The Contribute of CSF Free Ligh Chain assay in the diagnosis of Multiple Sclerosis and other Neurological Diseases in an Italian multicentric study (ID 1734)
Abstract
Background
Detection of IgG Oligoclonal bands (OCB) in CSF by Isoelectric focusing (IEF) is an important criteria for multiple sclerosis (MS) diagnosis. Recently, quantitative measurement of CSF Free Light Chains (FLC), has been proposed as a faster, standardized and cheaper alternative to detect intrathecal Immunoglobulin (Ig) synthesis. However, FLC indexes (FLCI) cut off often varies depending on the selected population, with a lack of consensus.
Objectives
To assess, in a large and heterogeneous population, the diagnostic accuracy of CSF k and λ FLC in MS and other neurological diseases.
Methods
406 patients were selected in 5 Italian centres. OCB were detected by IEF, followed by immunodetection, FLCs were measured in paired CSF (LFLC) and serum (SFLC) using Freelite MX assays on the Optilite turbidimeter (Binding Site), as well as serum (SAlb) and CSF Albumin (LAlb). FLCI= (LFLC/SFLC)/(LAlb/SAlb).
Results
Patients: 174 MS, 149 non-inflammatory neurological disorders (NIND), 50 inflammatory CNS disorders (IND), 33 peripheral neurological disorders (PIND). KFLCI was significantly higher in patients with MS compared to the other groups (p <0.0001). The best kFLCI cut off for the prediction of MS was 6.4 (kFLCI+) with a diagnostic accuracy comparable to OCB (sensitivity 82.2% vs 82,7%; specificity 88.4% vs 90,5%). 7% MS patients were kFLCI+ and OCB negative (-), 7% were kFLCI- and OCB positive (+), with 86% concordance of both tests. 40% IND were kFLCI+, 35% of which OCB-. 4% NIND were kFLCI+, with only 1 patient OBC+. 27% PIND were kFLCI+ and 21% OBC+. λFLCI values were higher in the MS group, but gave few additional information (optimal cut off 13.5). In MS group, OCB results were highly variable across the centres, while kFLC were more consistent, confirming that FLCI is less subject to personal interpretation.
Conclusions
Our findings support the combined use of KFLCI and OCB to detect intrathecal Ig synthesis. KFLCI can accurately discriminate MS from NIND and PIND patients. IND patients showed high KFLCI in higher proportion than OCB, hence clinical, imaging and other laboratory data are necessary for a correct diagnosis. On the other hand, OCB has technical limitations and showed high variability across the centres to support MS diagnosis. In conclusion, KFLC performances in our heterogeneous population, with patients coming from 5 geographically distinct centres, support the robustness of this test implying that it can be easily used across our country.