Isoelectric focusing followed by affinity immunoblotting to detect monoclonal free light chains in monoclonal gammopathies: Comparison with immunofixation electrophoresis and free light chain ratio.

BACKGROUND: Isoelectric focusing (IEF) is a method with an exquisite resolution, and coupled with affinity immunoblotting (AIB), it can provide superior sensitivity to detect monoclonal free light chains (FLC). METHODS: We tested the hypothesis that IEF/AIB is more sensitive and specific for monoclonal FLC detection in serum and urine samples than conventional methods, that is, electrophoresis (ELP), immunofixation (IF) and serum FLC ratio assessment. Investigation included 107 samples of 68 patients, among which 21 multiple myeloma patients were recently tested for minimal residual disease and 18 patients with AL amyloidosis. RESULTS: Monoclonal FLC were detected by IEF/AIB in 37% of serum samples negative for monoclonal FLC on ELP/IF. As for urine samples, significant advantage of the IEF/AIB over ELP/IF was not demonstrated. Considering both serum and urine results, IEF/AIB definitely revealed monoclonal FLC in 20/83 (24%) of ELP/IF-negative samples. FLC ratio was abnormally high (>1.65) in all 11 patients definitely positive for monoclonal FLC kappa by IEF/AIB but also in 16/47 (34%) IEF/AIB-negative samples. Abnormally low values (<0.26) were found only in 10/28 samples (36%) positive for monoclonal FLC lambda. Appropriate use of renal FLC ratio reference range reduced the number of presumably false positives (6/47, i.e. 13%) but not false negatives (17/28, i.e. 61%). CONCLUSIONS: The IEF/AIB method is more sensitive than IF and might be used in patients with negative IF results before deciding whether to proceed to minimal residual disease testing.

A comparison of measles-rubella-zoster reaction, oligoclonal IgG bands, oligoclonal kappa free light chains and kappa index in multiple sclerosis.

BACKGROUND AND OBJECTIVES: To evaluate the diagnostic performance of the measles-rubella-zoster reaction (MRZR) in a large real-world multiple sclerosis (MS) cohort. Second, to compare MRZR with the determination of oligoclonal IgG bands (OCB), oligoclonal kappa free light chain bands (oKFLC), and the KFLC index. METHODS: A single-center retrospective study was conducted at the University Hospital Ostrava (Czech Republic). Patients were eligible if aged ≥18 years with a determined clinical diagnosis. IgG antibodies against measles (M), rubella (R), and varicella zoster (Z) viruses were determined in paired CSF and serum using ELISA and MRZR indicated as positive if at least two components had an antibody index >1.4. OCB and oKFLC were detected by means of isoelectric focusing, and KFLC CSF and serum concentrations for calculation of the KFLC index were determined immunochemically. RESULTS: A total of 1,751 patients were included in the analyzed data set, which comprised 379 MS patients and 1,372 non-MS controls. The frequency of positive MRZR was higher in MS than in non-MS cases (MS 32.2 % vs non-MS 2.8 %; p < 0.001). This corresponded to a specificity of 97.2 % (95 % CI 96.1-98.0) and sensitivity of 32.2 % (95 % CI 27.5-37.2) and overall accuracy of 83.1 % (95 % CI 81.3-84.8). In comparison, the highest sensitivity of 95.6% (95 % CI 93.0-97.5) was for OCB with specificity of 86.9 % (95 % CI 84.9-88.7), followed by oKFLC with sensitivity and specificity of 94.7 % (95 % CI 91.5-96.9) and 78.4% (95 % CI 75.7-80.8), respectively, and the KFLC index with sensitivity of 92.5 % (95 % CI 86.6-96.3) and specificity of 93.5 % (95 % CI 90.5-95.9). DISCUSSION: MRZR remains a very specific test for the diagnosis of MS but has low sensitivity, which disallows its independent use. In contrast, OCB showed the highest sensitivity and thus remains the gold standard for the diagnosis of MS.

Successful treatment of SAPHO syndrome (chronic nonbacterial osteomyelitis and acne) with anakinra and denosumab. Case report and review of therapy.

SAPHO is an acronym derived from capital letters of Synovitis, Acne, Pustulosis, Hyperostosis, and Osteitis (SAPHO). SAPHO syndrome is an umbrella term covering a constellation of bone lesions and skin manifestations. A 40-year-old male complained about his jaw and back pain, swelling of multiple joints and weight loss accompanied by physical deterioration and acne type skin lesions. Laboratory tests revealed abnormal elevation of inflammatory markers. Imaging studies illustrated multiple osteolytic bone lesions and paraosseal infiltrates. According to the set of criteria diagnosis of SAPHO syndrome was stated. The patient was treated with glucocorticoids and non-steroidal anti-inflammatory drugs (NSAIDs), but only high dose dexamethasone and prednisone were effective. Daily subcutaneous administration of anakinra at the dose of 100 mg was initiated due to limited response to more classical therapies. Because of planned mandibular osteosynthesis initiation of denosumab was preferred before bisphosphonates. Therapeutic response was confirmed by FDG-PET/MR after 5 months of anakinra and denosumab therapy, showing decreased accumulation of FDG in periosteal and paraosseal infiltrates. Inflammatory markers significantly decreased, bone pain deferred but skin manifestation receded only partially. Therefore the response was evaluated as partial remission.

Cerebrospinal fluid neurofilament light chains and CXCL13 as predictive factors for clinical course of multiple sclerosis.

AIM: The aim of this study was to identify whether NfL and CXCL13 cerebrospinal fluid (CSF) concentrations at diagnostic lumbar puncture can predict the course of multiple sclerosis (MS) in terms of relapses, higher expanded disability status scale (EDSS) and magnetic resonance imaging (MRI) activity. METHODS: We conducted a single-centre prospective observational cohort study at the MS center, University Hospital Ostrava, Czech Republic. CSF NfL (cNfL) and CXCL13 concentrations were examined (ELISA method) in patients with clinically isolated syndrome (CIS) and relapsing-remitting MS (RRMS) at the time of diagnostic lumbar puncture. RESULTS: A total of 44 patients with CIS or early RRMS were enrolled, 31 (70.5%) of whom were women. The median age at the time of CSF sampling was 31.21 years (IQR 25.43-39.32), and the follow-up period was 54.6 months (IQR 44.03-59.48). In the simple and multiple logistic regression models, CXCL13 levels did not predict relapses, MRI activity or EDSS > 2.5. Similarly, cNfL concentrations did not predict relapses or MRI activity in either model. In the multiple regression, higher cNfL levels were associated with reaching EDSS > 2.5 (odds ratio [OR] 1.002, 95% confidence interval [CI] 1.000 to 1.003). CONCLUSIONS: Our data did not confirm cNfL and/or CXCL13 CSF levels were predictive factors for disease activity such as relapses and MRI activity at the time of diagnostic lumbar puncture in patients with RRMS. While cNfL CSF levels predicted higher disability only after adjustment for other known risk factors, elevated CSF CXCL13 did not predict higher disability at all.

Analysis of cerebrospinal fluid cells by flow cytometry: Comparison to conventional cytology.

AIMS: This study compared the results obtained by basic immunophenotyping of cerebrospinal fluid (CSF) cells by flow cytometry (FC) to the results of conventional cytology and evaluated the possibility of detailed analyses of CSF B-cell subpopulations. METHODS: Samples from 42 patients were examined by conventional cytology (native and/or pre-centrifuged CSF) and FC. The results from 15 patients without evidence of organic neurological disease were used to estimate reference ranges. RESULTS: Pre-centrifugated CSF had significantly higher cell yield on the cytologic slide, but cell subpopulation percentages were altered; the percentage of lymphocytes was significantly higher and monocytes significantly lower compared to both native CSF slides and FC. The percentage of granulocytes was higher in FC compared to cytology. For leukocyte count, the following reference ranges were estimated for Fuchs-Rosenthal chamber (FR) counting and FC, respectively: leukocytes ≤4.7/µL and ≤2.5/µL, lymphocytes ≤4.1/µL and ≤1.8/µL, monocytes ≤1.2/µL and ≤0.9/µL, and granulocytes 0/µL and ≤0.2/µL. The following reference ranges were estimated for basic subpopulations: T-lymphocytes 84.1-100%, B lymphocytes 0.0-1.5%, NK cells 0.0-6.3%, NKT cells 0-9.5%, and CD3+CD4+/CD3+CD8+ 0.8-4.9. Using a volume of 1.2-2.4 mL, the number of B lymphocytes was too low (<20) in samples with ≤2.7 cells/µL in the FR. CONCLUSIONS: Even normal CSF samples are amenable to basic mononuclear cell subpopulation analysis by FC. However, analysis of the B-cell subpopulations requires either a larger sample volume or selection of samples with ≥ 3 cells/µL.

IgG4-related disease. Clinical manifestation differential diagnosis and recent International Diagnostic Criteria for IgG4-related disease.

Immunoglobulin G4- related disease (IgG4-RD) is a rare systemic fibro-inflammatory disorder. Autoimmune pancreatitis is the most frequent manifestation of IgG4-RD. However, IgG4-RD can affect any organ such as salivary glands, orbits, retroperitoneum, prostate and many others. Recent research enabled a clear clinical and histopathological description of IgG4-RD and in 2019 four Clinical phenotypes of IgG4-related disease were described. Diagnosis is based on morphological examination with typical findings of lymphoplasmocellular inflammation, storiform fibrosis and obliterative phlebitis in IgG4-RD biopsies and the tissue invading plasma cells largely produce IgG4. Elevated serum IgG4 levels are found in many but not all patients. New diagnostic criteria for IgG4-RD have been published recently in 2019 and 2021. This review summarizes current knowledge on pathophysiology, clinical manifestations, diagnosis and differential diagnosis of IgG4-RD from the point of view 2022 and in next article brings overview of the IgG4-RD therapy.

Prognostic value of intrathecal IgM synthesis determined by various laboratory methods in patients with early multiple sclerosis - a prospective observational study.

BACKGROUND: Intrathecal IgM synthesis has been identified as an adverse prognostic factor in patients with multiple sclerosis (MS); however, some studies have not confirmed this association. The objective of this study was to evaluate the clinical utility of intrathecal IgM synthesis for prediction of disease activity and disability in patients after the first demyelinating event of MS. METHODS: We conducted a single-centre prospective observational cohort study at the Department of Neurology, University Hospital Ostrava, Czech Republic. Intrathecal IgM synthesis was demonstrated by the presence of cerebrospinal fluid-restricted oligoclonal IgM bands and calculated using the Reiber, Auer, and Öhman formula and IgM index. RESULTS: A total of 61 patients with a clinically isolated syndrome or early relapsing-remitting MS were enrolled into the analysis of which 37 (61 %) were women. The median age at the disease onset was 32 years (interquartile range [IQR] 25 - 42), and the median disease duration was 2.8 years (IQR 2.4 - 3.5). Thirty-eight (62 %) patients experienced a second relapse of MS with a median of 312 days (IQR 192 - 424), and 29 (47.5 %) developed magnetic resonance imaging (MRI) activity during the follow-up. Intrathecal IgM synthesis did not affect the risk of a second relapse or evidence of MRI activity in univariate and multivariate Cox regression analysis. There was no significant difference in disability using the Expanded Disability Status Scale and progression index in patients with or without intrathecal IgM synthesis. CONCLUSION: This prospective cohort study did not demonstrate that intrathecal IgM synthesis is a risk factor for a second relapse or MRI activity. It was not associated with higher disability in patients after the first demyelinating event.

Detection of monoclonal free light chains by immunofixation electrophoresis and isoelectric focusing - comparison with the quantitative method of determination.

The study aimed to investigate free light chain (FLC) monoclonality in patients with an abnormal free kappa/lambda ratio (FLC ratio). Seventy serum samples with abnormal FLC ratio were examined using an immunoturbidimetry (Binding Site, SPA) and the two different enzyme-linked immunosorbent assays (1. Sebia diagnostic kit; 2. in house methods), the monoclonal or oligoclonal bands of (FLC) by immunofixation electrophoresis (IE) and isoelectric focusing followed by affinity immunoblotting (IEF/AIB). The reference interval was calculated by non-parametric percentile method. 5.7% of samples examined by IE were suspected of monoclonal character of FLCs, but subsequently monoclonality was refuted by more sensitive IEF/AIB method; 7%, resp. 2.9% of samples showed FLC kappa, resp. FLC lambda oligoclonal character of bands. A statistically significant dependence was found between FLC ratio (Sebia) and FLC ratio (SPA), rs = 0.510, p = .001. Kappa statistic evaluated a fair conformity between the FLC ratio (Sebia) and IEF/AIB (kappa = 0.468) and between FLC ratio (in house) and IEF/AIB (kappa = 0.300). The verified reference interval for FLC ratio (Binding Site) is between 0.35 and 2.18. The IEF/AIB is the most sensitive method to discriminate between monoclonal and oligoclonal bands of FLC. The Binding Site and Sebia diagnostic kits do not give consistent results. The Binding Site diagnostic kit provides more results above reference interval of FLC ratios. For routine decision on monoclonality of the FLC ratio (SPA) it is advisable to use a verified reference interval.

Cerebrospinal fluid oligoclonal IgM test in routine practice: Comparison with quantitative assessment of intrathecal IgM synthesis.

BACKGROUND: Intrathecal IgM synthesis demonstrated either as cerebrospinal fluid (CSF)-restricted oligoclonal (o-) IgM bands or calculated using various formulas has been linked to more aggressive multiple sclerosis (MS) course. However, the proportion of MS patients showing intrathecal IgM synthesis varies largely between studies. We aimed to explore the relation between different formulas and results of o-IgM, and to assess the frequency of o-IgM bands in an unselected series of samples. METHODS: 432 samples were analyzed for o-IgM, o-IgG and quantitative measures of IgM and IgG synthesis. IgM index and formulas of Reiber, Auer and Öhman were compared to the result of the o-IgM test. RESULTS: At the cut-off commonly used, the non-linear formulas for intrathecal synthesis were specific (>94%) but rather insensitive (<40% even at a cut-off of 4 CSF-restricted bands) compared to o-IgM. No significant difference was noted in the performance of different formulas. At a cut-off of 4 bands, 61% of MS patients, but none of the controls were positive for o-IgM. CONCLUSIONS: Formulas for intrathecal IgM synthesis are insensitive compared to o-IgM. We propose to evaluate samples with 2 or 3 extra-CSF IgM bands as borderline and only samples with 4 or more as definitely positive.

Determination of chitinase 3-like 1 in cerebrospinal fluid in multiple sclerosis and other neurological diseases.

OBJECTIVES: Chitinase 3-like 1 (CHI3L1) is an extracellular monomeric single-chain glycoprotein expressed by many types of cells. Its elevated levels were found in cerebrospinal fluid in central nervous system (CNS) inflammatory diseases patients. The aim of the study was 1) to validate the reference interval of cerebrospinal fluid (CSF) CHI3L1 in a control group; 2) to measure the CHI3L1 concentration in different diagnosis groups .including multiple sclerosis (MS); and 3) to correlate those values with other biomarkers of axonal damage or neuroinflammation in different grous. METHODS: The study included 132 CSF samples sent to the Department of Clinical Biochemistry, Institute of Laboratory Diagnostics, University Hospital Ostrava. Concentrations of CHI3L1, CXCL13 chemokine, neurofilament light chains, and phosphorylated neurofilament heavy chains were determined by enzyme-linked immunosorbent assays. IgG oligoclonal bands were detected by isoelectric focusing in agarose gels followed by immunofixation. IgM and FLC oligoclonal bands were analyzed by IEF followed by affinity immunoblotting. The group consisted of 42 patients with multiple sclerosis, 14 with clinically isolated syndrome, 11 with other central nervous system inflammatory diseases, 46 with non-inflammatory diseases of the central nervous system, 4 with inflammatory diseases of the peripheral nervous system, and 15 controls. RESULTS: The estimated reference values of CHI3L1 were 28.6-182.5 µg.L-1. Statistically significant differences of CSF CHI3L1 concentrations were found among diagnosis groups (p < 0.0001), after age adjustment (p = 0.002). There was a statistically significant relationship between CHI3L1 and NFL in the MS group (rs = 0.460; P = 0.002), and between CHI3L1 and pNFH in the MS group (rs = 0.691; P < 0.001). No statistically significant difference was found in the categorical comparison of CHI3L1 in the MS group and other diagnostic groups as well as when using the Mann-Whitney U test for CHI3L1 with additional parameters with and without oligoclonal bands present. CONCLUSIONS: CSF CHI3L1 values differ depending on diagnosis and correlate significantly with concentrations of the axonal damage markers CSF neurofilament light chains, and CSF phosphorylated neurofilament heavy chains, but not with CSF concentrations of the inflammatory marker CXCL13. Thus, CSF CHI3L1 could be another promising prognostic, albeit probably etiologically nonspecific, biomarker of MS.

Diagnostic relevance of free light chains in cerebrospinal fluid - The hyperbolic reference range for reliable data interpretation in quotient diagrams.

BACKGROUND: Free light chains, type kappa (FLC-K), in cerebrospinal fluid (CSF) were compared to oligoclonal IgG in many studies for sensitive detection of immune reactions in brain. The missing consensus about CSF data interpretation prevents reliable conclusions. This can be overcome by a theory-based hyperbolic reference range in CSF/serum quotient diagrams. METHODS: Mean Quotients for FLC-K, QKappa, and albumin, QAlb, of grouped, biochemically defined controls (N = 433) are fitted with the hyperbolic function QKappa(mean) = a/b (QAlb2 + b2)0.5 - c by a generally applicable procedure excluding outliers. RESULTS: With QKappa(mean), the coefficient of variation CV (22.5%) and the reference range (QKappa(mean) ±â€¯3 CV) we got the discrimination line QKappa(lim) = (3.27(QAlb2 + 33)0.5-8.2) ×10-3 in a FLC-K Reibergram. Intrathecal FLC-K was found in 8% of another control group without OCB (N = 388) but was missed in 7% of patients with definite Multiple sclerosis (N = 95). In MS the mean intrathecal fraction was threefold larger for FLC-K (95%) compared to total IgG (36%). Similar mean quantities of intrathecal FLC-K contradict an immunological conversion between a Clinically isolated syndrome and MS. DISCUSSION: The hyperbolic reference range is superior to linear FLC-K Index (10 to 15% false negatives) and exponential curves (30% false positive interpretations for controls) in the analytical range of MS data, with excellent data fit for up to ten-fold larger QAlb values. Dynamics of the small molecule FLC-K contribute to the understanding of molecular size dependent barrier functions.

Neurofilament levels in patients with neurological diseases: A comparison of neurofilament light and heavy chain levels.

BACKGROUND: Neurofilaments are the major cytoskeletal components of neurons, and cell injury leads to their release into the surrounding area. The aim of this study was to compare the cerebrospinal fluid (CSF) and serum (S) concentrations of neurofilament light chains (NFLs) and phosphorylated neurofilament heavy chains (pNFHs). METHODS: Neurofilament concentrations were measured in CSF and S samples from 172 patients using three enzyme-linked immunosorbent assays. Excel, Stata version 13, MedCal version 17.9.7., and NCSS 2007 software were used for the statistical analysis. RESULTS: There was a statistically significant correlation between the concentrations of CSF NFL and CSF pNFH (rs  = 0.748; n = 89; P < 0.001), but Passing-Bablok regression showed systematic deviation between the values obtained using the two assays. This indicates that the assays were not interchangeable. CSF pNFH and S pNFH concentrations showed low correlation. The kappa statistic showed moderate conformity between CSF pNFH and CSF NFL concentrations (κ = 0.556). CONCLUSIONS: The CSF NFL and CSF pNFH assays gave clinically consistent results that reflected the degree of axonal damage, independent of any particular neurological diagnosis. The S pNFH assays had a lower predictive value due to the low correlation coefficient and the kappa index of the CSF pNFH method.

Chemiluminescent detection of oligoclonal immunoglobulins after isoelectric focusing and affinity-mediated immunoblotting.

BACKGROUND AND AIMS: Detection of oligoclonal IgG (o-IgG) in the cerebrospinal fluid (CSF) not found in serum is the principal laboratory test to support a diagnosis of multiple sclerosis. The aim of this study was to compare chemiluminescent and chromogenic detection of oligoclonal immunoglobulins in the cerebrospinal fluid and serum after their separation by means of isoelectric focusing followed by immunoblotting. METHODS: A set of experiments was designed to detect oligoclonal immunoglobulins by means of alkaline phosphatase BCIP/NBT substrate and chemiluminescent peroxidase substrate. RESULTS: Based on visual evaluation of signals, chemiluminescent detection requires about a 4 times lower amount of applied protein than very sensitive BCIP/NBT chromogenic detection. Very good correlation between methods has been shown for oligoclonal IgG. Antigen-specific oligoclonal IgG could be demonstrated by both methods although the pattern was clearer using chemiluminescence. In one patient, oligoclonal IgD bands barely visible by BCIP/NBT were convincingly demonstrated by chemiluminescence. CONCLUSION: Chemiluminescent detection is a feasible option for oligoclonal immunoglobulin detection and could be used in cases when the sensitivity needs to be improved. Further studies and method optimisation are warranted.

Quantitation of IgG kappa and IgG lambda in the cerebrospinal fluid by sandwich ELISA method.

IgG kappa and IgG lambda concentrations were quantified in 96 paired CSF and sera using Hevylite™ antibodies in an in-house developed sandwich ELISA method. In 56 of these samples, the results were compared with a qualitative isoelectric focusing/affinity-mediated immunoblotting assay for oligoclonal IgG kappa and IgG lambda. Normal IgG kappa/lambda ratio in the CSF was the same as in serum. In 19/33 patients with intrathecal oligoclonal IgG synthesis, skewed IgG kappa/lambda ratio was observed (increased in 16 and decreased in 3 cases). The analysis of light chain composition of intrathecally synthesised immunoglobulins could contribute to our understanding of intrathecal humoral immune response, although its diagnostic utility is limited.

Assessment of Intrathecal Free Light Chain Synthesis: Comparison of Different Quantitative Methods with the Detection of Oligoclonal Free Light Chains by Isoelectric Focusing and Affinity-Mediated Immunoblotting.

OBJECTIVES: We aimed to compare various methods for free light chain (fLC) quantitation in cerebrospinal fluid (CSF) and serum and to determine whether quantitative CSF measurements could reliably predict intrathecal fLC synthesis. In addition, we wished to determine the relationship between free kappa and free lambda light chain concentrations in CSF and serum in various disease groups. METHODS: We analysed 166 paired CSF and serum samples by at least one of the following methods: turbidimetry (Freelite™, SPAPLUS), nephelometry (N Latex FLC™, BN ProSpec), and two different (commercially available and in-house developed) sandwich ELISAs. The results were compared with oligoclonal fLC detected by affinity-mediated immunoblotting after isoelectric focusing. RESULTS: Although the correlations between quantitative methods were good, both proportional and systematic differences were discerned. However, no major differences were observed in the prediction of positive oligoclonal fLC test. Surprisingly, CSF free kappa/free lambda light chain ratios were lower than those in serum in about 75% of samples with negative oligoclonal fLC test. In about a half of patients with multiple sclerosis and clinically isolated syndrome, profoundly increased free kappa/free lambda light chain ratios were found in the CSF. CONCLUSIONS: Our results show that using appropriate method-specific cut-offs, different methods of CSF fLC quantitation can be used for the prediction of intrathecal fLC synthesis. The reason for unexpectedly low free kappa/free lambda light chain ratios in normal CSFs remains to be elucidated. Whereas CSF free kappa light chain concentration is increased in most patients with multiple sclerosis and clinically isolated syndrome, CSF free lambda light chain values show large interindividual variability in these patients and should be investigated further for possible immunopathological and prognostic significance.

Increased albumin quotient (QAlb) in patients after first clinical event suggestive of multiple sclerosis is associated with development of brain atrophy and greater disability 48 months later.

BACKGROUND: The utility of blood-brain barrier (BBB) biomarkers for clinical and magnetic resonance imaging progression in multiple sclerosis (MS) has not been extensively investigated. OBJECTIVES: To determine whether cerebrospinal fluid (CSF) measures of BBB at clinical onset predict radiological and clinical deterioration over 48 months. METHODS: This longitudinal study included 182 patients after first clinical event suggestive of MS treated with weekly intramuscular interferon beta-1a. CSF and serum samples were analyzed for leukocytes, total protein, albumin, immunoglobulins, and oligoclonal bands. Optimal thresholds for the albumin quotient (QAlb) were determined. Mixed-effect model analyses, adjusted for age, gender, and treatment escalation, were used to analyze relationship between CSF measures and disease activity outcomes over 48 months of follow-up. RESULTS: Increased QAlb at clinical onset was associated with enlargement of lateral ventricles (p = .001) and greater whole brain (p = .003), white matter (p < .001), corpus callosum (p < .001), and thalamus (p = .003) volume loss over 48 months. Higher QAlb was associated with higher Expanded Disability Status Scale score over 48 months (p = .002). CONCLUSIONS: Increased QAlb at clinical onset is associated with increased brain atrophy and greater disability in patients after first clinical event suggestive of MS.

Quantitation of free light chains in the cerebrospinal fluid reliably predicts their intrathecal synthesis.

BACKGROUND: The results of free light chains quantitation in the cerebrospinal fluid were recently compared with the presence of cerebrospinal fluid-restricted oligoclonal IgG, but not oligoclonal free kappa light chains and oligoclonal free lambda light chains. We therefore aimed to compare the performance of the quantitative tests with the qualitative one for the same molecule. METHODS: Seventy-five paired cerebrospinal fluid and serum samples were analysed for oligoclonal IgG, oligoclonal free kappa light chains and oligoclonal free lambda light chains. Cerebrospinal fluid and serum free kappa and lambda light chains were quantified using Freelite™ kits on SPA Plus analyzer. ROC curves were analysed for the prediction of intrathecal synthesis and compared for cerebrospinal fluid concentration, cerebrospinal fluid/serum quotient (QfLC) and index (QfLC/QAlbumin). The presence of cerebrospinal fluid-restricted oligoclonal free kappa light chains and oligoclonal free lambda light chains bands was used as reference. RESULTS: No statistically significant differences were observed among cerebrospinal fluid concentration, QfLC and index for the prediction of free light chain intrathecal synthesis. Each parameter was able to predict the occurrence of cerebrospinal fluid-restricted oligoclonal free light chain bands (AUCs 0.932-0.999). However, we noted elevated cerebrospinal fluid free light chain concentrations in the absence of cerebrospinal fluid-restricted oligoclonal free light chain bands in two patients with very high serum free light chain values. CONCLUSIONS: Quantitation of cerebrospinal fluid free light chains reliably predicts their intrathecal synthesis. Yet, cerebrospinal fluid/serum quotient may still be preferred to correct for high serum free light chain concentrations. An appropriate formula should be sought to correct for blood-cerebrospinal fluid barrier status.

Oligoclonal free light chains in cerebrospinal fluid as markers of intrathecal inflammation. Comparison with oligoclonal IgG.

AIMS: To compare the sensitivity and specificity of CSF-restricted oligoclonal IgG and free light chains as markers of multiple sclerosis and other inflammatory neurological diseases. METHODS: 196 paired CSF and serum samples were examined for oligoclonal IgG and oligoclonal free light chains. The sensitivity and specificity of the tests were calculated and optimal cut-offs for the number of CSF-restricted oligoclonal bands were then determined by analysis of receiver operating characteristic curves. RESULTS: Optimal cut-off values were ≥5 IgG bands for multiple sclerosis, ≥4 IgG bands for inflammatory neurological disease, ≥6 free κ, and ≥2 free λ bands for both purposes. Using these cut-off values, sensitivities and specificities for multiple sclerosis were 83.8% and 91.3% for IgG, 83.8% and 81.0% for free κ, and 67.6% and 75.4% for free λ. For inflammatory neurological disease, sensitivities and specificities were 60.8% and 95.7% for IgG, 69.6% and 92.6% for free κ, and 64.8% and 86.2% for free λ. CONCLUSIONS: Although exact cut-off values may vary according to method, reporting borderline results as positive, may compromise the specificity of the test and should be avoided.. The detection of intrathecal free light chain synthesis may be of value especially when the oligoclonal IgG test is negative or borderline, even though its specificity is slightly lower.