The Increasing Role of Kappa Free Light Chains in the Diagnosis of Multiple Sclerosis.

Free light chains (FLC) are a promising biomarker to detect intrathecal inflammation in patients with inflammatory central nervous system (CNS) diseases, including multiple sclerosis (MS). The diagnostic use of this biomarker, in particular the kappa isoform of FLC ("KFLC"), has been investigated for more than 40 years. Based on an extensive literature review, we found that an agreement on the correct method for evaluating KFLC concentrations has not yet been reached. KFLC indices with varying cut-off values and blood-CSF-barrier (QAlbumin) related non-linear formulas for KFLC interpretation have been investigated in several studies. All approaches revealed high diagnostic sensitivity and specificity compared with the oligoclonal bands, which are considered the gold standard for the detection of intrathecally synthesized immunoglobulins. Measurement of KFLC is fully automated, rater-independent, and has been shown to be stable against most pre-analytic influencing factors. In conclusion, the determination of KFLC represents a promising diagnostic approach to show intrathecal inflammation in neuroinflammatory diseases. Multicenter studies are needed to show the diagnostic sensitivity and specificity of KFLC in MS by using the latest McDonald criteria and appropriate, as well as standardized, cut-off values for KFLC concentrations, preferably considering non-linear formulas such as Reiber's diagram.

Silver Nanoparticles as a Tool for the Study of Spontaneous Aggregation of Immunoglobulin Monoclonal Free Light Chains.

Some misfolded proteins, e.g., immunoglobulin monoclonal free light chains (FLC), tend to form fibrils. Protein deposits in tissue may lead to amyloidosis and dysfunction of different organs. There is currently no technique allowing for the identification of FLC that are prone to aggregate. The development of such a method would enable the early selection of patients at high risk of developing amyloidosis. The aim of this study was to investigate whether silver nanoparticles (AgNPs) could be a useful tool to study the process of aggregation of FLC and their susceptibility to form the protein deposits. Mixtures of AgNPs and urine samples from patients with multiple myeloma were prepared. To evaluate the aggregation process of nanoparticles coated with proteins, UV-visible spectroscopy, transmission electron microscopy, and the original laser light scattering method were used. It has been shown that some clones of FLC spontaneously triggered aggregation of the nanoparticles, while in the presence of others, the nanoparticle solution became hyperstable. This is probably due to the structure of the chains themselves, unique protein-AgNPs interactions and perhaps correlates with the tendency of some FLC clones to form deposits. Nanoparticle technology has proven to be helpful in identifying clones of immunoglobulin FLC that tend to aggregate.

Application of Capillary Electrophoresis in Monoclonal Gammopathies and the Cutoff Value of Monoclonal Protein in Differential Diagnosis of Multiple Myeloma and Other Monoclonal Gammopathies.

OBJECTIVE: Monoclonal protein (MP) exists in various diseases, and capillary electrophoresis (CE) has been widely used to detect MP. However, there is not much research on the application value of MP in the differential diagnosis of monoclonal gammopathies. This study aimed to explore MP's cutoff value for the differential diagnosis of multiple myeloma (MM) and other monoclonal gammopathies (MGs). METHODS: A retrospective analysis of 8167 cases was conducted. Serum MP was detected by CE, and the patients' clinical information was collected from the clinical database of our hospital. RESULTS: 985 cases had MP with high peaks, and 91.1% were diagnosed with malignant diseases. The MP showed small peaks in 471 cases, and only 24.4% were diagnosed with malignant diseases. Among the MPs, the IgG-κ type was the most common type, followed by the IgG-λ, IgA-κ, IgA-λ, free λ light chain, IgM-κ, free κ light chain, double clone, and IgM-λ types. Differences in the MP of the IgG, IgA, IgM, and FLC types between the MM group and MGUS group were statistically different (P<0.01). The MP of the IgG, IgA, and FLC types showed clear specificity and sensitivity in discriminating MM from other monoclonal gammopathies in ROC curve analysis. Serum IgM had statistical significance in the differential diagnosis between WM and other MGs (P<0.01). However, there was no statistical significance in the differential diagnosis between MM and other MGs (P=0.140). The cutoff values of the MP of the IgG, IgA, and FLC types were >18.67g/L, >13.86g/L, and >10.15g/L, respectively, for the differential diagnosis of MM and other MGs. The cutoff value of the MP of IgM for the WM diagnosis was >37.75 g/L. CONCLUSION: CE has good clinical application value in the diagnosis of monoclonal gammopathies, and MP can be used in the differential diagnosis of MM and other monoclonal gammopathies.

A rare case of IgE kappa monoclonal gammopathy of undetermined significance identified in a Swedish female.

Monoclonal gammopathies involving immunoglobulin E (IgE) is a very rare phenomenon, with less than 70 cases being previously described in the literature. The IgE monoclonal gammopathies include malignant plasma cell disorders such as IgE multiple myeloma (MM), as well as the associated premalignant condition IgE monoclonal gammopathy of undetermined significance (MGUS). We report a case of a 41-year-old woman presenting with an IgE kappa monoclonal protein following routine laboratory testing. Serum protein electrophoresis (SPEP) initially showed a monoclonal protein in the beta-2 fraction, at an estimated concentration of <4 g/L. Subsequent serum immunofixation electrophoresis (SIFE) including antisera to Ig heavy chains delta and epsilon confirmed the presence of an IgE kappa monoclonal protein. Analysis of serum free light chains (FLCs) showed increased levels of kappa FLC, resulting in an abnormally elevated kappa/lambda FLC ratio. No Bence-Jones proteinuria was present. Bone marrow aspiration showed 6% plasma cells, and no sign of myeloma-associated end-organ damage was evident. Consequently, the patient was diagnosed with IgE kappa MGUS. In the present report, the clinical characteristics of the patient are compared to previous descriptions of IgE monoclonal gammopathy. The report further emphasizes the importance of considering the presence of monoclonal IgD or IgE when SIFE shows a clear band positive for a light chain but is negative for Ig heavy chains gamma, alpha and mu.

Serum and urine free light chains measurements in patients with systemic sclerosis: novel biomarkers for disease activity.

Circulating free light chains (FLCs), considered biomarkers of B cell activity, are frequently elevated in patients affected by systemic inflammatory autoimmune diseases. As the systemic sclerosis (SSc) clinical course can be variable, this study is aimed at evaluating FLCs levels in affected individuals as biomarkers of disease activity. We assessed FLC levels in serum and urine of 72 SSc patients and 30 healthy controls (HC). Results were analyzed in comparison with overall clinical and laboratory findings, disease activity index (DAI) and disease severity scale (DSS). SSc patients displayed increased levels of κ and λ FLC in serum significantly higher than HC (p = 0.0001) alongside the mean values of free κ/λ ratio and κ + λ sum (p = 0.0001). SSc patients showed increased free κ in urine with a κ/λ higher than HC (p = 0.0001). SSc patients with increased κ + λ in serum showed that erythro-sedimentation rate (p = 0.034), C-reactive protein (p = 0.003), DAI (p = 0.024) and DSS (p = 0.015) were higher if compared to SSc patients with normal levels of FLC. A positive linear correlation was found between serum levels of free κ and DAI (r = 0.29, p = 0.014). In addition, SSc patients with increased free κ in urine had higher DAI (p = 0.048) than SSc patients with normal κ levels. Our results strengthen the role of serum FLC as useful biomarker in clinical practice to early diagnosis and monitor disease activity, showing for the first time that also urine FLC levels correlated with disease activity in SSc patients.

Baseline serum B-cell maturation antigen levels predict time to disease progression for patients with smoldering multiple myeloma.

Multiple myeloma (MM) patients with smoldering (S) disease are defined by a lack of CRAB/SLiM criteria but may transform into disease requiring treatment. The International Myeloma Working Group risk stratification model for SMM uses serum M-protein, serum-free light chain ratio, and bone marrow plasma cell percentage. We investigated whether baseline serum B-cell maturation antigen (sBCMA) levels are predictive of disease progression among 65 patients with SMM. A receiver operating characteristic curve was used to establish a definition for high-risk baseline sBCMA. Mantel Byar analysis was used to examine whether high-risk sBCMA was correlated with shorter time to transformation, and a time-dependent cox proportional hazard was used to determine whether it is independent of other risk factors. A z test for proportions was used to compare the percentage of patients that progressed among high-risk versus low-risk sBCMA patients. A baseline sBCMA level ≥137.5 mg/ml was found to be the optimal cutoff between high- and low-risk SMM patients. Patients with high-risk sBCMA levels had a shorter time to transformation (P = .000332). sBCMA was also higher at the time of transformation than baseline levels (P = .0116). sBCMA was the only variable found to be significantly predictive of time to transformation and additionally was found to be independent of other risk factors. In this study, we have shown for the first time that sBCMA levels predict transformation of SMM to active disease and that these levels increase at the time of transformation. These results are consistent with other studies showing that active MM patients undergoing therapy with higher baseline sBCMA levels are more likely to progress early and its levels increase at the time of disease progression.

Kappa Free Light Chains in the Context of Blood Contamination, and Other IgA- and IgM-Related Cerebrospinal Fluid Disease Pattern.

In this retrospective, monocentric cohort study, we tested if an intrathecal free light chain kappa (FLC-k) synthesis reflects not only an IgG but also IgA and IgM synthesis. We also analysed if FLC-k can help to distinguish between an inflammatory process and a blood contamination of cerebrospinal fluid (CSF). A total of 296 patient samples were identified and acquired from patients of the department of Neurology, University Medicine Greifswald (Germany). FLC-k were analysed in paired CSF and serum samples using the Siemens FLC-k kit. To determine an intrathecal FLC-k and immunoglobulin (Ig) A/-M-synthesis we analysed CSF/serum quotients in quotient diagrams, according to Reiber et al. Patient samples were grouped into three cohorts: cohort I (n = 41), intrathecal IgA and/or IgM synthesis; cohort II (n = 16), artificial blood contamination; and the control group (n = 239), no intrathecal immunoglobulin synthesis. None of the samples had intrathecal IgG synthesis, as evaluated with quotient diagrams or oligoclonal band analysis. In cohort I, 98% of patient samples presented an intrathecal synthesis of FLC-k. In cohort II, all patients lacked intrathecal FLC-k synthesis. In the control group, 6.5% presented an intrathecal synthesis of FLC-k. The data support the concept that an intrathecal FLC-k synthesis is independent of the antibody class produced. In patients with an artificial intrathecal Ig synthesis due to blood contamination, FLC-k synthesis is lacking. Thus, additional determination of FLC-k in quotient diagrams helps to discriminate an inflammatory process from a blood contamination of CSF.

MASS-FIX for the detection of monoclonal proteins and light chain N-glycosylation in routine clinical practice: a cross-sectional study of 6315 patients.

Immunoenrichment-based matrix assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS), termed MASS-FIX, offers several advantages over immunofixation for the detection and isotyping of serum monoclonal protein, including superior sensitivity and specificity, the ability to differentiate therapeutic monoclonal antibodies, and the rapid identification of light chain (LC) N-glycosylation. We identified 6315 patients with MASS-FIX performed at our institution since 2018. Of these, 4118 patients (65%) with a wide array of plasma cell disorders (PCD), including rare monoclonal gammopathies of clinical significance, had a positive MASS-FIX. Two-hundred twenty-one (5%) of the MASS-FIX positive patients had evidence of LC N-glycosylation, which was more commonly identified in IgM heavy chain isotype, kappa LC isotype, and in diagnoses of immunoglobulin light chain (AL) amyloidosis and cold agglutinin disease (CAD) compared to other PCD. This cross-sectional study describes the largest cohort of patients to undergo MASS-FIX in routine clinical practice. Our findings demonstrate the widespread utility of this assay, and confirm that LC N-glycosylation should prompt suspicion for AL amyloidosis and CAD in the appropriate clinical context.

Serum free light chain reference intervals in an Optilite and their influence on clinical guidelines.

BACKGROUND: Serum free light chain (FLC) analysis has been incorporated into the International Myeloma Working Group guidelines for the diagnosis and management of all monoclonal gammopathies. These recommendations were solely based on a single assay method (Freelite assay) and instrument. Here, we establish new reference intervals (RIs) for kappa and lambda FLC and the kappa-lambda difference and sum and a new diagnostic range for kappa/lambda FLC ratio (K/L-FLC) in an Optilite turbidimeter (The Binding Site) with the Freelite assay. METHODS: To establish new RIs, the CLSI EP28-A3C protocol was applied to 249 sample blood donors from Fuenlabrada, Spain, and the central 95% and total range were estimated. Samples from patients with polyclonal hypo- and hypergammaglobulinemia were used for the evaluation of K/L-FLC as a monoclonal proliferation index. RESULTS: The new RIs and the new K/L-FLC diagnostic range for the Optilite (0.65-2.56 mg/L) are very different from those in on the guidelines (0.26-1.65 mg/L). We propose new RIs for the K - L difference and the K + L sum. Diagnostic range validation as a monoclonal proliferation index with samples with hypo- and hypergammaglobulinemia confirms this new range. CONCLUSIONS: In this study, we present the FLC RI for Freelite reagents measured on an Optilite turbidimeter. These ranges are different from those provided by the manufacturer and from those used in most studies in the literature, which may lead to patient misclassification. Manufacturers and clinical laboratories must strive to provide RIs for the technology they are using and for their population.

Hematological and Genetic Markers in the Rational Approach to Patients With HCV Sustained Virological Response With or Without Persisting Cryoglobulinemic Vasculitis.

BACKGROUND AND AIMS: Direct-acting antivirals (DAAs) usually lead to improvement/remission of cryoglobulinemic vasculitis (CV), although symptoms may persist/recur after a sustained virological response (SVR). We evaluated hematological and genetic markers in patients with HCV-SVR vasculitis with and without persisting/recurring symptoms to early predict the CV outcome. APPROACH AND RESULTS: Ninety-eight patients with HCV-CV were prospectively enrolled after a DAA-induced SVR: Group A: 52 with complete clinical response; Group B: 46 with symptom maintenance/recurrence. Monoclonal B-cell lymphocytosis, t(14;18) translocation, and abnormal free light chains κ/λ ratios were detected by flow cytometry or nested-PCR or nephelometry in 4% Group A versus 17% Group B (P = 0.04) patients, 17% Group A versus 40% Group B patients (P = 0.02), and 17% Group A versus 47% Group B (P = 0.003) patients, respectively. At least 1 out of 3 clonality markers was altered/positive in 29% of Group A versus 70% of Group B patients (P < 0.0001). When available, pretherapy samples were also tested for t(14;18) translocation (detected in 12/37 [32%] Group A and 21/38 [55%] Group B) and κ/λ ratios (abnormal in 5/35 [14%] Group A and 20/38 [53%] Group B) (P = 0.0006), whereas at least one clonality marker was detected/altered in 16/37 (43%) Group A and 30/38 (79%) Group B (P = 0.002). CV-associated single-nucleotide polymorphisms were tested by real-time PCR. Among them, notch4 rs2071286 T minor allele and TT genotype showed a higher frequency in Group B versus Group A (46% vs. 29%, P = 0.01, and 17% vs. 2%, P = 0.006, respectively). CONCLUSIONS: Hematological or genetic analyses could be used to foresee the CV clinical response after DAA therapy and could be valuable to assess a rational flowchart to manage CV during follow-up.

The Pivotal Role of Viruses in the Pathogeny of Chronic Lymphocytic Leukemia: Monoclonal (Type 1) IgG K Cryoglobulinemia and Chronic Lymphocytic Leukemia Diagnosis in the Course of a Human Metapneumovirus Infection.

BACKGROUND: Type-1 cryoglobulinemia (CG) is a rare disease associated with B-cell lymphoproliferative disorder. Some viral infections, such as Epstein-Barr Virus infections, are known to cause malignant lymphoproliferation, like certain B-cell lymphomas. However, their role in the pathogenesis of chronic lymphocytic leukemia (CLL) is still debatable. Here, we report a unique case of Type-1 CG associated to a CLL transformation diagnosed in the course of a human metapneumovirus (hMPV) infection. CASE PRESENTATION: A 91-year-old man was initially hospitalized for delirium. In a context of febrile rhinorrhea, the diagnosis of hMPV infection was made by molecular assay (RT-PCR) on nasopharyngeal swab. Owing to hyperlymphocytosis that developed during the course of the infection and unexplained peripheral neuropathy, a type-1 IgG Kappa CG secondary to a CLL was diagnosed. The patient was not treated for the CLL because of Binet A stage classification and his poor physical condition. CONCLUSIONS: We report the unique observation in the literature of CLL transformation and hMPV infection. We provide a mini review on the pivotal role of viruses in CLL pathophysiology.

Immunoglobulin D-kappa multiple myeloma in a patient with rheumatoid arthritis: a case report and review of the literature.

A 77-year-old Japanese woman with a 21-year history of seropositive, erosive rheumatoid arthritis (RA) and a 10-year history of methotrexate (MTX) therapy was admitted with malaise and mild consciousness disturbance. Laboratory data showed hypercalcemia, acute kidney injury, normocytic anaemia, and thrombocytopenia. As we first assumed drug-induced toxicity by MTX and eldecalcitol, both were discontinued and leucovorin rescue therapy and calcitonin were administered. However, her condition continued to worsen. Serum protein electrophoresis showed only a small M-peak, immunoelectrophoresis of both the serum and urine demonstrated Bence-Jones kappa (κ) type monoclonal protein without immunoglobulin heavy chain, and bone marrow examination revealed proliferation of plasma cells. We diagnosed her with Bence-Jones κ type multiple myeloma (MM) and transferred her to the department of haematology of a higher order medical institution. Conclusively, the diagnosis of immunoglobulin (Ig) D-κ type MM, a rare variant of this disorder, was determined in accordance with serum immunofixation. Several previous studies have suggested that pre-existing RA is a risk factor for MM. Although IgD MM is characterised by its clinical severity and poor prognosis compared to other subtypes, it is often misdiagnosed or mistaken as light chain type MM, as in the present case, because of the low level of IgD M-protein, resulting in delayed diagnosis. Physicians must take MM into consideration as a differential diagnosis when inactive RA patients present with inexplicable elevated calcium, renal failure, anaemia, and bone lesion symptoms and should be aware of IgD MM to establish the correct diagnosis promptly.

Biomarkers of minimal residual disease in rituximab-treated patients with mixed cryoglobulinemia.

Hepatitis C virus (HCV) represents the major risk factor for mixed cryoglobulinemia (MC), a small-vessel vasculitis that may evolve into an overt B-cell non-Hodgkin's lymphoma. Here, we aimed to identify a biomarker signature for the early diagnosis of minimal residual disease (MRD). We assessed free light chains (FLCs), IgM k,and IgM λ heavy/light chain (HLC) pairs, and vascular endothelial growth factor (VEGF) in sera from 34 patients with MC vasculitis (32 HCV- and 2 HBV-related), treated with low-dose rituximab (RTX). FLCs and IgM HLCs were measured by turbidimetric assay; VEGF by an enzyme-linked immunosorbent assay. After RTX, the positive (complete + partial) clinical and laboratory responses were of 85.29% and 50%, respectively; in contrast, the mean levels of FLCs, IgM HLCs, and VEGF were substantially unaffected in most patients and still above the normal range. In those achieving a reduction of FLCs and IgM k and λ chains values within the range of normality, we found that post-treatment free λ chains and IgM k values correlated with clinical and laboratory response. Our results suggest that high levels of FLCs, IgM HLCs, and VEGF could represent the signature of "dormant" B cell clones' activity that could be very useful to identify MRD indicative of possible relapse or worsening outcome.

Efficacy of Medium Cut-Off Dialyzer and Comparison with Standard High-Flux Hemodialysis.

BACKGROUND: A new medium cut-off (MCO) membranes has been designed to achieve better removal capacities for middle and large middle molecules in hemodialysis (HD) treatment. AIM: The aim of this study was to evaluate the removal efficacy of Theranova® in standard HD in comparison with standard high-flux HD. METHODS: Four HD patients (M/F 1/4) were included in 12-week observational pilot study in HD with Theranova® 400 and Theranova® 500 dialyzers. Each patient was assessed 4 times, T0 with high-flux dialyzers, T1 at 1 month, T2 at second month, and T3 at third month, by measuring pre- and post-HD samples of urea, Cr, ß2-microglobilin (ß2M), myoglobin, albumin, free light chains kappa (FLC-k), and free light chains lambda (FLC-λ). RESULTS: The data showed a higher average removal rate for all the uremic toxins with Theranova® dialyzers for ß2M, myoglobin, FLC-k, and FLC-λ (62.7, 56.9, 63.5, and 54.6%, respectively) during the 3 months. Albumin retention was observed and did not change between T0 and T3 (p = 0.379). CONCLUSION: Compared to high-flux membranes, MCO membranes show greater permeability for middle molecules in midterm report.

Intrathecal kappa free light chains as markers for multiple sclerosis.

Cerebrospinal fluid (CSF) kappa free light chain (KFLC) index has been described as a reliable marker of intrathecal IgG synthesis to diagnose multiple sclerosis (MS). Our aims were: (1) to compare the efficiency of KFLC through different interpretation approaches in diagnosing MS. (2) to evaluate the prognostic value of KFLC in radiologically and clinically isolated syndromes (RIS-CIS). We enrolled 133 MS patients and 240 with other neurological diseases (93 inflammatory including 18 RIS-CIS, 147 non-inflammatory). Albumin, lambda free light chain (LFLC) and KFLC were measured in the CSF and serum by nephelometry. We included two groups of markers: (a) corrected for blood-CSF barrier permeability: immunoglobulin G (IgG), KFLC and LFLC indexes. (b) CSF ratios (not including albumin and serum-correction): CSF KFLC/LFLC, CSF KFLC/IgG, CSF LFLC/IgG. KFLC were significantly higher in MS patients compared to those with other diseases (both inflammatory or not). KFLC index and CSF KFLC/IgG ratio showed high sensitivity (93% and 86.5%) and moderate specificity (85% and 88%) in diagnosing MS. RIS-CIS patients who converted to MS showed greater KFLC index and CSF KFLC/IgG. Despite OB are confirmed to be the gold-standard to detect intrathecal IgG synthesis, the KFLC confirmed their accuracy in MS diagnosis. A "kappa-oriented" response characterizes MS and has a prognostic impact in the RIS-CIS population.