Free light chains in the cerebrospinal fluid. Comparison of different methods to determine intrathecal synthesis.

Background Free light chains (FLC) have been proposed as diagnostic biomarkers in the cerebrospinal fluid (CSF) of patients with inflammatory central nervous system (CNS) diseases. However, which method to use for determining an intrathecal FLC synthesis has not yet been clarified. The objective of this study was to compare the diagnostic performance of CSF FLC concentration, FLC quotient (QFLC), FLC index and FLC intrathecal fraction (FLCIF). Methods κ- and λ-FLC were measured by nephelometry under blinded conditions in CSF and serum sample pairs of patients with clinically isolated syndrome (CIS; n = 60), multiple sclerosis (MS; n = 60) and other neurological diseases (n = 60) from four different MS centers. QFLC was calculated as the ratio of CSF/serum FLC concentration, the FLC index as QFLC/albumin quotient and the percentage FLCIF by comparing QFLC to a previously empirically determined, albumin quotient-dependent reference limit. Results CSF FLC concentration, QFLC, FLC index and FLCIF of both the κ- and λ-isotype were significantly higher in patients with CIS and MS than in the control group, as well as in oligoclonal bands (OCB) positive than in OCB negative patients. Each parameter was able to identify MS/CIS patients and OCB positivity, however, diagnostic performance determined by receiver operating characteristic (ROC) analyses differed and revealed superiority of FLC index and FLCIF. Conclusions These findings support the diagnostic value of FLC measures that correct for serum FLC levels and albumin quotient, i.e. blood-CSF barrier function.

Cerebrospinal fluid free light chains as diagnostic biomarker in neuroborreliosis.

BACKGROUND: Free light chains (FLC) have been proposed as diagnostic biomarker in patients with inflammatory central nervous system diseases. The objective of this study was to investigate the diagnostic utility of intrathecal κ- and λ-FLC synthesis in patients with neuroborreliosis. METHODS: κ- and λ-FLC were measured by nephelometry under blinded conditions in cerebrospinal fluid (CSF) and serum sample pairs of 34 patients with neuroborreliosis and compared to a cohort of 420 control patients. κ-FLC index was calculated as [CSF κ-FLC/serum κ-FLC]/[CSF albumin/serum albumin], and λ-FLC index in analogy. RESULTS: κ-FLC and λ-FLC index were significantly elevated in patients with neuroborreliosis compared to the control group. At a specificity level of 95%, κ-FLC and λ-FLC index showed a diagnostic sensitivity of 88.2% and 100%. In comparison, IgM and IgG synthesis according to Reiber formula, IgG index >0.7 and OCB status reached a sensitivity of 83.9%, 44.1%, 58.8% and 64.7%. CONCLUSION: These findings support the diagnostic value of intrathecal FLC synthesis in neuroborreliosis patients and demonstrate a valid, easy and rater-independent alternative for the detection of an intrathecal immunoglobulin production.

Validation of kappa free light chains as a diagnostic biomarker in multiple sclerosis and clinically isolated syndrome: A multicenter study.

BACKGROUND: Kappa free light chains (KFLCs) have been proposed as a diagnostic biomarker in patients with clinically isolated syndrome (CIS) and multiple sclerosis (MS). OBJECTIVE: The objective of this paper is to validate the diagnostic accuracy of intrathecal KFLC synthesis in a multicenter study. METHODS: KFLCs were measured by nephelometry under blinded conditions in cerebrospinal fluid (CSF) and serum sample pairs of patients with CIS (n = 60), MS (n = 60) and other neurological diseases (n = 60) from four different MS centers. The upper normal limit for intrathecal KFLC concentrations depending on blood-CSF barrier function was previously calculated in a cohort of 420 control patients. RESULTS: Diagnostic sensitivity of intrathecal KFLC synthesis, IgG synthesis according to Reiber, IgG index and oligoclonal bands (OCBs) was 95%, 72%, 73% and 93% in patients with MS and 82%, 47%, 43% and 72% in patients with CIS. Specificity of intrathecal KFLC synthesis was 95% and 98% for all other measures. CONCLUSION: These findings further support the diagnostic value of intrathecal KFLC synthesis in CIS and MS patients and demonstrate a valid, easier and rater-independent alternative to OCB detection.

A mutation in VPS35, encoding a subunit of the retromer complex, causes late-onset Parkinson disease.

To identify rare causal variants in late-onset Parkinson disease (PD), we investigated an Austrian family with 16 affected individuals by exome sequencing. We found a missense mutation, c.1858G>A (p.Asp620Asn), in the VPS35 gene in all seven affected family members who are alive. By screening additional PD cases, we saw the same variant cosegregating with the disease in an autosomal-dominant mode with high but incomplete penetrance in two further families with five and ten affected members, respectively. The mean age of onset in the affected individuals was 53 years. Genotyping showed that the shared haplotype extends across 65 kilobases around VPS35. Screening the entire VPS35 coding sequence in an additional 860 cases and 1014 controls revealed six further nonsynonymous missense variants. Three were only present in cases, two were only present in controls, and one was present in cases and controls. The familial mutation p.Asp620Asn and a further variant, c.1570C>T (p.Arg524Trp), detected in a sporadic PD case were predicted to be damaging by sequence-based and molecular-dynamics analyses. VPS35 is a component of the retromer complex and mediates retrograde transport between endosomes and the trans-Golgi network, and it has recently been found to be involved in Alzheimer disease.

VPS35 Parkinson's disease phenotype resembles the sporadic disease.

Recently a new autosomal dominant Parkinson's disease mutation (p.Asp620Asn) in the VPS35 gene was discovered. The clinical features of 14 PD patients with this mutation from three Austrian families were evaluated. Age at disease-onset appears lower and depression was more common in Austrian patients compared to sporadic PD patients. However, we were unable to identify a specific clinical maker of VPS35 patients, who otherwise resemble sporadic PD patients.

Diagnostic value of kappa free light chain index in patients with primary progressive multiple sclerosis - a multicentre study.

Background: Kappa free light chains (κ-FLC) in the cerebrospinal fluid (CSF) are an emerging biomarker in multiple sclerosis (MS). Objective: To investigate whether κ-FLC index has similar diagnostic value in patients with primary progressive multiple sclerosis (PPMS) compared to oligoclonal bands (OCB). Methods: Patients with PPMS were recruited through 11 MS centres across 7 countries. κ-FLC were measured by immunonephelometry/-turbidimetry. OCB were determined by isoelectric focusing and immunofixation. Results: A total of 174 patients (mean age of 52±11 years, 51% males) were included. κ-FLC index using a cut-off of 6.1 was positive in 161 (93%) and OCB in 153 (88%) patients. Conclusion: κ-FLC index shows similar diagnostic sensitivity than OCB in PPMS.

Elevated levels of kappa free light chains in CSF support the diagnosis of multiple sclerosis.

BACKGROUND: Numerous studies have demonstrated elevated kappa free light chains (KFLCs) in CSF of multiple sclerosis (MS) patients. However, so far only small cohorts have been examined, and generally only through qualitative KFLCs analysis. Using a recently developed free light chain (FLC) immunoassay, it is now possible to quantitatively measure KFLCs by automated nephelometry. Our objective was to determine the extent to which KFLC levels in CSF correlated with the diagnosis of MS and CISSMS (clinically isolated syndrome suggestive of MS) compared to oligoclonal banding (OCB) and the immunoglobulin G (IgG) index. METHODS: CSF and serum samples from 438 unselected patients, including a MS group of 70 patients (41 MS, 29 CISSMS), were analysed using nephelometry and isoelectric focusing. We then retrospectively correlated results with patients' diagnoses. RESULTS: Of the MS group (n = 70), 67 patients had elevated KFLCs using the KFLC index (> or = 5.9), 64 patients showed OCB and 56 patients presented with an elevated IgG index (> or = 0.6). Sensitivities were 0.96 for the KFLC index, 0.91 for OCB and 0.80 for the IgG index. The specificity of the KFLC index for the MS group (0.86) was lower than that of OCB (0.92) but distinctly higher compared to the IgG index (0.77). CONCLUSION: In this study, an elevated KFLC-index represented the most sensitive and specific quantitative diagnostic parameter for MS. As it is measured by automated, routinely available laboratory methods, KFLC quantitation can provide a rapid and reproduceable indication of intrathecal immunological processes supporting current MS diagnostic criteria.

RasGAP-like protein IQGAP1 is expressed by human keratinocytes and recognized by autoantibodies in association with bullous skin disease.

Autoantibodies in patients with autoimmune bullous skin diseases, such as pemphigus or bullous pemphigoid are of diagnostic value and might play a part in the pathogenic scenario. In this study we present five patients with erythematous plaques, subepidermal blister formation of the skin, and the presence of circulating autoantibodies directed against a so far unrecognized 190 kDa antigen in human keratinocytes. Amino acid sequence analysis identified the protein as IQGAP1, a recently described human Ras GTPase-activating-like protein suspected to act as an effector molecule for Cdc42 and Rac1, members of the Rho small GTPase family and to play a key part in regulating E-cadherin-mediated cell adhesion. The protein is selectively recognized by a monoclonal anti-IQGAP1 antibody on western blots and immunoprecipitates from keratinocyte extracts. Indirect immunofluorescence locates IQGAP1 within individual keratinocytes in a cytoplasmic pattern and along the cell periphery at adhesive sites. Our results demonstrate IQGAP1, a newly described multifunctional protein, to be constitutively expressed in human keratinocytes where it may contribute to the integrity of the epidermal layer. Furthermore, we found autoantibodies reacting with IQGAP1 in patients with bullous skin eruptions most apparently belonging to the spectrum of bullous pemphigoid.

Kappa free light chains: diagnostic and prognostic relevance in MS and CIS.

BACKGROUND: Quantification of kappa free light chains (KFLC) in cerebrospinal fluid shows high diagnostic sensitivity in multiple sclerosis and clinically isolated syndrome patients. However, a clearly defined threshold value is still missing and a possible prognostic value of the KFLC levels in these patients remains undefined. METHODS: Results of KFLC quantification in 420 controls were used to set an upper limit of normal KFLC concentration in CSF under different blood-CSF-barrier conditions. Additionally, KFLC values of MS and CIS patients were assessed and results were evaluated with reference to the patients corresponding disease courses. RESULTS: The calculated upper limit of normal KFLC-concentration covers 98% of these control patients. Using this cut-off, plasma cell activity in CSF can be detected in 97% of MS patients and in 97% of CIS patients. However, there is no evidence that the extent of KFLC elevation provides prognostic value in MS and CIS patients in this study. CONCLUSION: KFLC determination should become a first line screen in the diagnostic algorithms of MS and CIS. The extent of elevation of intrathecal KFLC has no prognostic value on the disease course in MS and CIS patients.

Cerebrospinal fluid immunoglobulin kappa light chain in clinically isolated syndrome and multiple sclerosis.

BACKGROUND: Oligoclonal bands (OCB) are the most widely used CSF test to support the diagnosis of MS and to predict conversion of clinically isolated syndrome (CIS) to multiple sclerosis (MS). Since OCB tests are based on non-quantitative and difficult to standardise techniques, measurement of immunoglobulin kappa free light chains (KFLC) may represent an easier to use quantitative test. METHODS: KFLC were measured in CSF and serum of 211 patients using ELISA. These include patients without any inflammatory central nervous system reaction (NIND, n = 77), MS (n = 20), viral CNS infections (V-CNS-I, n = 10), neuroborreliosis (NB, n = 17) and other bacterial CNS infections (B-CNS-I, n = 10). Furthermore a cohort of 77 patients with CIS, including 39 patients that remained CIS over follow-up of two years (CIS-CIS) and 38 patients that developed MS over the same follow-up time (CIS-MS). RESULTS: CSF-serum ratio of KFLC (Q KFLC) was elevated in all patients with MS, 86.8% of patients with CIS-MS and 61.5% of patients with CIS-CIS. It was significantly elevated in CIS with presence of OCB (p<0.001). Q KFLC significantly correlated with other CSF variables such as CSF leukocyte count (p<0.001, R = 0.46), CSF CXCL13 levels (p<0.001, R = 0.64) and also intrathecal IgG synthesis (p<0.001, R = 0.74) as determined by nephelometry and quotient diagram. OCB were detected in 66.7% of CIS-CIS and in 92.1% of CIS-MS. CONCLUSIONS: Although the measurement of CSF KFLC is a rapid and quantitative easy to standardize tool, it is almost equal but not superior to OCB with regard to diagnostic sensitivity and specificity in patients with early MS.