ABSTRACT
BACKGROUND AND OBJECTIVES: Kappa free light chains (KFLC) seem to efficiently diagnose MS. However, extensive cohort studies are lacking to establish consensus cut-offs, notably to rule out non-MS autoimmune CNS disorders. Our objectives were to (1) determine diagnostic performances of CSF KFLC, KFLC index, and KFLC intrathecal fraction (IF) threshold values that allow us to separate MS from different CNS disorder control populations and compare them with oligoclonal bands' (OCB) performances and (2) to identify independent factors associated with KFLC quantification in MS. METHODS: We conducted a retrospective multicenter study involving 13 French MS centers. Patients were included if they had a noninfectious and nontumoral CNS disorder, eligible data concerning CSF and serum KFLC, albumin, and OCB. Patients were classified into 4 groups according to their diagnosis: MS, clinically isolated syndrome (CIS), other inflammatory CNS disorders (OIND), and noninflammatory CNS disorder controls (NINDC). RESULTS: One thousand six hundred twenty-one patients were analyzed (675 MS, 90 CIS, 297 OIND, and 559 NINDC). KFLC index and KFLC IF had similar performances in diagnosing MS from nonselected controls and OIND (p = 0.123 and p = 0.991 for area under the curve [AUC] comparisons) and performed better than CSF KFLC (p < 0.001 for all AUC comparisons). A KFLC index of 8.92 best separated MS/CIS from the entire nonselected control population, with better performances than OCB (p < 0.001 for AUC comparison). A KFLC index of 11.56 best separated MS from OIND, with similar performances than OCB (p = 0.065). In the multivariate analysis model, female gender (p = 0.003), young age (p = 0.013), and evidence of disease activity (p < 0.001) were independent factors associated with high KFLC index values in patients with MS, whereas MS phenotype, immune-modifying treatment use at sampling, and the FLC analyzer type did not influence KFLC index. DISCUSSION: KFLC biomarkers are efficient tools to separate patients with MS from controls, even when compared with other patients with CNS autoimmune disorder. Given these results, we suggest using KFLC index or KFLC IF as a criterion to diagnose MS. CLASSIFICATION OF EVIDENCE: This study provides Class III evidence that KFLC index or IF can be used to differentiate patients with MS from nonselected controls and from patients with other autoimmune CNS disorders.
Subject(s)
Central Nervous System Diseases , Demyelinating Diseases , Multiple Sclerosis , Female , Humans , Immunoglobulin kappa-Chains , Oligoclonal Bands , Demyelinating Diseases/diagnosis , Biomarkers , Cohort StudiesABSTRACT
The complement system is composed of a set of plasma or membrane proteins. Complement protein deficiencies can be inherited or acquired, through the presence of autoantibodies or through consumption. We evaluated the analytical performance of the Optilite® analyser for the determination of the C3 and C4 levels and for the evaluation of the total complement activity. The intra- and inter-series CVs were evaluated and have showed satisfactory results, the concordances with analysers currently used in the laboratory (BNII® and BCT®, Siemens) are very good, as is the agreement between the serum and plasma samples. We also determined the reference values for the different parameters tested in view of a routine use of Optilite® analyser in the laboratory.
Subject(s)
Complement C3/analysis , Complement C4/analysis , Complement System Proteins/analysis , Hematologic Tests/instrumentation , Adult , Artifacts , Automation, Laboratory/instrumentation , Automation, Laboratory/standards , Blood Chemical Analysis/instrumentation , Blood Chemical Analysis/methods , Blood Chemical Analysis/standards , Blood Coagulation/physiology , Complement C3/metabolism , Complement C4/metabolism , Complement System Proteins/metabolism , Equipment Contamination , Hematologic Tests/methods , Hematologic Tests/standards , Humans , Reference Standards , Reproducibility of ResultsABSTRACT
This retrospective analysis was conducted in 64 patients diagnosed with type I cryoglobulinaemia (CG) followed at two French centres. Median follow-up was 6·75 years. CG was IgG in 60% and IgM in 40% of all cases and was asymptomatic in 16 patients (25%). Cold-triggered ischaemic skin manifestations were observed in 33 patients (51%). Neurological manifestations were observed in 15 patients and renal manifestations in 13. Most of the patients with necrotic purpura (14/16, P = 0·009) and renal manifestations (11/13, P = 0·057) had IgG CG. IgG CG was associated with monoclonal gammopathy of undetermined significance (MGUS), myeloma, chronic lymphocytic leukaemia and lymphoplasmocytic lymphoma in 18, 13, 5 and 2 patients, respectively. IgM CG was associated with MGUS and Waldenström macroglobulinaemia in 8 and 18 cases, respectively. One third of patients did not receive any specific treatment. Various treatments, including rituximab, were administered to 25/31 patients with IgG CG and 6/25 patients with IgM CG due to CG-related symptoms. Rituximab was ineffective in all cases associated with a predominantly plasmacytic proliferation. To conclude, type I CG has specific clinico-biological characteristics compared to type II CG. Furthermore, there are differences in terms of related manifestations between type I IgG and type I IgM CG.
