Determination Of Free Light Chains Research Articles

AMYLOID CARDIOMYOPATHY: DIAGNOSIS AND TREATMENT

The review presents current data on heart disease in systemic amyloidosis. The article discusses variants of amyloi-dosis with common heart disease: AL-, ATTRwt- and ATTRv amyloidoses. Clinical signs of amyloid cardiomyopathy and extracardiac manifestations that allow one to suggest amyloidosis are described. Methods for diagnosing amyloid cardiomyopathy are presented. Echocardiographic diagnostic characters include increased thickness of the left ventricular wall, atrioventricular valve, right ventricular wall, thickening of the interatrial septum, and also diastolic dysfunction, and decreased global longi-tudinal strain with relative preservation of apical longitudinal strain. Magnetic resonance imaging reveals signs specific for amyloidosis: increased extracellular volume and diffuse suben-docardial or transmural delayed enhancement after gadolinium administration. Scintigraphy using technetium-99m labeled compounds can confirm the diagnosis of ATTR cardiomyopathy. The diag-nosis of ATTR cardiomyopathy is only possible in combination with blood and urine tests to exclude the presence of a monoclonal protein. Screening for monoclonal protein includes three laboratory tests: determination of free light chains in blood serum, electrophoresis of serum protein and urine protein with immunofixation. Indications for myocardial biopsy and the role of extracardiac tissue biopsy are discussed. Endomyocardial biopsy should be performed: a) in case of strong clinical suggestion of cardiac amyloidosis in a patient with monoclonal pro-tein; b) in case of strong clinical suggestion of cardiac amyloidosis, despite negative or equivocal scintigraphy result; c) if cardiac scintigraphy is not available. The possibilities of pathogenetic therapy for ATTR- and AL amyloidosis, aimed at stopping or slowing amyloid deposi-tion in the heart, and symptomatic treatment are discussed.

Diagnostic value of the saliva immunoglobulin free light chains concentrations measured in primary Sjцgren's syndrome

Proliferation and hyperactivation of B-lymphocytes in the salivary glands is a feature of primary Sjцgren's syndrome (pSS). Detection in saliva of proteins synthesized by B-lymphocytes may be important in the diagnosis of this disease.Objective: to evaluate the diagnostic value of measuring the concentration of immunoglobulin free light chains (FLC) in saliva in patients with pSS.Material and methods. The cross-sectional study included 24 patients with pSS over the age of 18 years. PSS was diagnosed according to the 2016 ACR/EULAR classification criteria. The control group consisted of 11 healthy volunteers. Blood-salivary glands histohematic barrier permeability ratio for albumin, FLC was measured. Quantitative determination of FLC and in blood and saliva was performed by enzyme immunoassay. An immunohistochemical study of biopsies of minor salivary glands (MSG) was carried out with a quantitative assessment of CD3+, CD4+, CD8+, CD20+, CD21+, CD68+, CD138+ cells. The Mann–Whitney U-test was used to compare quantitative traits. Identification of diagnostic thresholds for the concentration of FLC in saliva for the diagnosis of pSS was carried out using the ROC analysis method. An operating characteristic curve was plotted, the area under the curve, indicators of diagnostic specificity, diagnostic sensitivity, and diagnostic accuracy were calculated.Results and discussion. The obtained values corresponded to the low permeability of the histohematic barrier of the salivary glands for albumin and FLC in patients with pSS and healthy individuals. The median concentrations of FLC ê and ë in the saliva of patients with pSS and healthy volunteers were 1.08 [0.58; 1.91], 1.038 [0.55; 2.03] mg/l and 0.36 [0.32; 0.54], 0.35 [0.21; 0.52] mg/l, respectively. The concentration of FLC in the saliva of patients with pSS was statistically significantly higher than in the control group (p<0.01). The amount of FLC ê and ë in saliva correlated with the rate of unstimulated saliva flow: rs=-0.483 (p=0.02), rs=-0.491 (p=0.017), respectively.A relationship was found between the concentration of ê-chains in saliva and the specific number of CD138+ cells: rs=0.733 (p=0.025). Statistically significant correlations between the concentration of ë-chains and the number of mononuclear cells in the MSG have not been established.Based on the results of ROC analysis, diagnostic thresholds for FLC concentrations in the saliva of patients with pSS were determined. Concentrations of ê- and ë-type FLC in saliva of 0.56 and 0.68 mg/l correspond to area under the curve values of 0.84 (95% confidence interval, CI 0.69–0.98) and 0.83 (95% CI 0.71–0.97), sensitivity 79.2% (95% CI 59.5–90.8) and 75% (95% CI 55.1–88), specificity 81.8% (95% CI 52.3–96.8) and 90.9% (95% CI 62.3–99.5), respectively.Salivary FLC concentrations were compared in patients with pSS receiving and not receiving glucocorticoids (GC). The groups did not differ in a statistically significant way in terms of clinical and laboratory parameters. The median daily dose of GC was 10 [5; 10] mg in prednisolone equivalent. There were no significant differences between the concentrations of saliva FLC in patients of these groups.Conclusion. Salivary-fixed FLCs are most likely produced by cells localized in the stroma of the salivary glands. Determination of the concentration of FLC in saliva can be proposed as a diagnostic test for the pSS. The concentration of free ê-chains in saliva can be considered as a surrogate marker of benign B-cell proliferation in the MSG. Therapy with low and medium doses of GC in pSS does not affect the concentration of FLC in saliva.

Systemic forms of amyloidosis with cardiac manifestation

The term amyloidosis summarizes heterogeneous diseases in which a misfolding of protein structures occurs. These misfolded proteins can fundamentally be deposited anywhere in the body and lead to malfunction of the affected organ. There are preferential sites of deposition depending on which protein is misfolded. Cardiac transthyretin (ATTR) amyloidosis is a rare cause of cardiomyopathy and part of an underdiagnosed systemic disease. For cardiac ATTR amyloidosis, which involves deposition of misfolded tranthyretin either as a wild type (wtATTR) or as a mutated form (mATTR or hATTR), evidence-based treatment options have recently become available with slowing of the progression of the cardiomyopathy and a significant reduction of hospitalization rates. Therefore, it is important to diagnose this severe disease at an early stage and to differentiate it from other forms of amyloidosis. A clinical screening is easily possible by determination of free light chains using imaging examinations (cardiac magnetic resonance imaging or scintigraphic procedures) and immunofixation before the definitive diagnosis is made based on a biopsy and/or genetic tests. An interdisciplinary work-up involving hemato-oncology, nephrology, neurology and other disciplines, is indispensable when cardiac amyloidosis is suspected.

Reference Intervals for Plasma Free Kappa and Lambda Chains and Kappa/Lambda Ratio using PENIA.

Determination of free light chains is used increasingly for patients with multiple myeloma and other plasma cell dyscrasias. The aim of the present study was to define reference intervals for free kappa and lambda chains and kappa/lambda ratio in lithium heparin plasma and compare the test results with cystatin C based estimated glomerular filtration rate. Free kappa and lambda chains were measured in Liheparin plasma from 222 healthy blood donors using free light chain reagents and a BNII nephelometer from Siemens Diagnostics. Calculated reference intervals for kappa chain, free was 4.73 mg/L (90% confidence interval 4.00 - 5.45) - 22.66 mg/L (20.33 - 24.98), for lambda chain, free was 4.33 mg/L (3.70 - 4.95) - 29.28 mg/L (26.96 - 31.59), and for Kappa/Lambda Chain ratio 0.59 (0.56 - 0.62) - 1.46 (1.37 - 1.56). There was no need for gender or age specific reference intervals. Cystatin C based estimated glomerular filtration rate had a significant effect on the levels of free light chains. The study presents reference intervals for plasma free light chains and compared results of estimated glomerular filtration rate with free light chains of kappa and lambda.

Biochemical profile of Bence-Jones type multiple myeloma.

Multiple myeloma (MM) is a malignant tumor occurring from plasma cells that produce an abnormal monoclonal immunoglobulin - a paraprotein. A distinctive feature of Bence-Jones myeloma is the excretion of monoclonal free light chains of immunoglobulins with 24h urine, and the absence of monoclonal intact immunoglobulins secretion. Comprehensive analysis of biochemical parameters in blood serum and 24h urine in patients with Bence-Jones multiple myeloma using electrophoretic and immunoturbidimetric methods to assess their sensitivity as biomarkers. 50 patients with a morphologically confirmed diagnosis of MM of the Bence-Jones immunochemical type were examined. 28 people without oncological diseases were examinedas a control. Detection of monoclonal secretion in blood serum and daily urine was performed by immunofixation electrophoresis on the Hydrasys 2 electrophoretic system (Sebia). The determination of free light chains of immunoglobulins (FLC) was performed by the immunoturbidimetric method (Binding Site) on an Advia 1800 analyzer (Siemens). Analysis of IgG, IgA, IgM, β2-microglobulin and C-reactive protein was performed on Cobas 6000 analyzer (Roche). The median excretion of Bence-Jones protein in 24h urine of MM patients was 0.49 g/24h (0.06-2.45 g/24h). In the blood serum, in 86% of cases, the presence of paraproteinemia, represented by κ and λ type light chains of immunogloublins was detected. At the same time, the frequency of detection of monoclonal secretion in blood serum in Bence-Jones type λ myeloma was 95.7%, which was statistically significantly higher than the frequency of detection of monoclonal secretion of type κ - 77.8%. In patients with identified paraproteinemia, Bence-Jones protein excretion in daily urine (median 0.82 g/day) was statistically significantly higher than in patients without a monoclonal component detected in blood serum (median 0.04 g/24h). The levels of FLC in blood serum obtained by immunoturbidimetry in Bence-Jones myeloma of the corresponding type were higher than the reference levels in 100% of cases. The median level of κ-FLC reached 4358 mg/l, λ-FLC - 2225 mg/l, which was statistically significantly higher than the control levels. The median concentrations of IgG, IgA and IgM in patients with Bence-Jones myeloma were statistically significantly lower than in the control group, while the medians of β2-microglobulin and C-reactive protein were significantly higher than in the control. Our investigation showed high diagnostic efficiency of electrophoretic and immunoturbidimetric analysis of monoclonal secretion in patients with Bence-Jones MM, while FLC analysis demonstrated maximum sensitivity. Bence-Jones MM revealed biochemical signs of secondary immunodeficiency and general inflammatory syndrome.

Accuracy of determination of free light chains (Kappa and Lambda) in plasma and serum by Swedish laboratories as monitored by external quality assessment

BackgroundFree light chain (FLC) measurements are important in diagnosing monoclonal gammopathies. As FLC are heterogeneous, different reagents and instruments for measuring FLC concentrations may give diverging results that affect assessment of patients with monoclonal gammopathies. Here we investigated agreement between different FLC methods using data from the Swedish external quality assurance (EQA) programme. MethodsThe two main FLC assays, N Latex FLC (Siemens) and Serum Freelite (The Binding Site), using four nephelometric or turbidimetric instrument platforms, were compared. Results from 27 EQA rounds distributed to 11–16 Swedish hospital laboratories during 2015–2020 were investigated. ResultsThe kappa (κ) FLC measurements deviated significantly over time, but when only nephelometry was used, deviation from the mean was lower (median ranges: −5% to 13 %). The CV was significantly higher for the Freelite assay (mean CV = 8.7) than for the N latex assay (mean CV = 5.7) (p < 0.0001). The coefficient of determination between all combinations of reagents and instrument platforms used was generally good (r2 = 0.76–0.87), and the correlation slope acceptable (0.81–1.2). For lambda (λ) FLC measurements, no concordance between combinations of instruments and reagents is apparent, deviating between −40 % to + 48 % from the mean. The CV was significantly higher for the combination with nephelometry and the Freelite assay (CV mean = 13.9 %) than nephelometry and the N latex assay (CV mean = 9.9 %) (p <0.001). The coefficient of determination varied between combinations of reagents and instrument platforms (r2 = 0.59–0.89) and the slope ranged between 0.48 and 1.5. Significant differences between the two reagents used were sometimes noted. ConclusionsImprecision in λFLC affects the κFLC/λFLC ratio. This may be important in clinical assessment of patients, especially differentiating between monoclonal and polyclonal gammopathies.

240 Serum polyclonal free light chains: possible markers of immune activation in psoriasis

The aim of this study was to investigate the role of polyclonal free light chains (FLCs) of the immunoglobulins as markers of immune activation in the management of psoriatic patients on treatment with biologics. The overall study population included 30 patients affected by mild-to- severe psoriasis with either ongoing biological treatment or without any current systemic therapy and 10 healthy controls. FLCs, which include κ and λ chains, were determined by quantitative nephelometric assay while antinuclear antibodies (ANA) through immunofluorescence. Psoriatic patients showed significant increased levels of κ and λ FLCs compared to healthy controls. Interestingly, κ and λ FLCs values were significantly increased only in psoriatic patients with ongoing biological treatment and in particular in responder subjects. Furthermore, correlation of both κ and λ FLCs with duration of therapy showed significant results. Patients with FLC levels above the normality range and under biological treatment for more than 12 months showed higher odds to be ANA+ respect to patients with FLC levels above the normality range but under biological treatment for less than 12 months. Increased FLCs levels would seem to act as markers of immune reactivation in psoriatic patients on treatment with biologic agents suggesting that the determination of FLCs could have clinical relevance in psoriasis clinical management

Immunoglobulin free light chains as a diagnostic and prognostic biomarker in multiple sclerosis: A real life study

Cerebrospinal fluid (CSF) immunoglobulin free light chains (FLCs) have been proposed as a quantitative and automatable alternative to oligoclonal bands (OCBs) with a potential role as predictor of Multiple Sclerosis (MS) severity. The aim of the study is to evaluate the utility of FLC determination in the initial assessment of patients with suspected MS as a diagnostic and prognostic biomarker.

The importance of serum immunoglobulin free light chain assessment for predicting outcome in patients with newly diagnosed multiple myeloma in real clinical practice

Background. The prognosis of patients with multiple myeloma (MM) is significantly different depending on the biological characteristics of the tumor substrate, the microenvironment of the bone marrow, as well as factors associated with the patient’s body. Therefore, the search for new reliable and easily identifiable prognostic markers is relevant for the effective management of patients with this disease.The objective of the study was to assess the prognostic value of the study of serum free light chains (FLC) of immunoglobulins κ and λ and their ratio κ / λ FLC in the blood serum of patients with newly diagnosed MM in real clinical practice.Materials and methods. 369 patients with first diagnosed MM (134 men and 235 women) were examined who were hospitalized in the hematology department of the City Clinical Hospital No. 2 Novosibirsk in the period since January 2012 to December 2017. The median age of the patients was 67 (32–82) years. All patients received induction courses of chemotherapy based on bortezomib. The control group consisted of 56 conditionally healthy individuals: 34 women (60.7 %) and 22 (39.3 %) men with a median age of 62 (40–68) years. The concentration of FLC-κ and FLC-λ (mg / L) in blood serum was determined by immunoturbidimetric method on a Hitachi 911 automated biochemical analyzer using the Freelite Human Lambda and Freelite Human Kappa reagent kits (Binding Site, Great Britain).Results. It was found that in patients with MM, the concentration of serum FLC-κ or FLC-λ was statistically significantly higher compared to the control group and varied depending on the type of MM (p &lt;0.001). The diagnostic sensitivity of the quantitative determination of FLC and their ratio for MM was 98.64 %, compared with 94.04 % in a standard immunochemical study. The values of the ratio κ / λ FLC &lt;0.04 or&gt; 65, as well as the concentration of FLC-κ and FLC-λ are higher than the median obtained in the whole group (FLC-κ ≥702 mg / L and FLC-λ ≥493.2 mg / L), correlate with known factors of poor prognosis for MM (with a high concentration of β2‑microglobulin (&gt;3.5 mg / L) (r = 0.461; p &lt;0.001), plasma cell bone marrow infiltration &gt;60 % (r = 0.420; p &lt;0.001), renal failure (creatinine &gt;177 μmol / L) (r = 0.380; p = 0.002), and also with high lactate dehydrogenase activity (&gt;450 U / L) (r = 0.520; p &lt;0.001) and is associated with poor outcomes. The median overall survival in the group of patients with κ / λ FLC &lt;0.04 or &gt;65 was 49 months compared to 76 months in the group with κ / λ FLC 0.04–65 (log-rank p = 0.012).Conclusion. The determination of free FLC in the blood serum of patients with MM can be used to assess the prognosis of their survival. The value of the κ / λ FLC ratio &lt;0.04 or &gt;65 allows us to divide patients with MM into risk groups with significantly different outcomes and can be used to identify patients at high risk who need more aggressive therapy and more detailed monitoring of the response.

Determination of free light chains: assay-dependent differences in interpretation.

Determination of free light chains: assay-dependent differences in interpretation.

Suspected cardiac amyloidosis - diagnostic steps for evaluation

Cardiac amyloidosis is a rare cause of cardiomyopathy, however, it is part of an underdiagnosed underlying systemic disease. For transthyretin (ATTR) amyloidosis, which is caused by the deposition of incorrectly folded transthyretin, either as the wild-type (wtATTR) or mutated (mATTR) form, novel evidence-based treatment options were recently shown to reduce disease progression as well as hospitalisation rates for heart failure. Thus, it is important to establish early and reliable diagnosis of cardiac involvement with ATTR amyloidosis.Modern non-invasive imaging (cardio magnetic resonance (CMR) and scintigraphic methods) together with immune fixation with determination of free light chains allow fast and reliable clinical screening for cardiac amyloidosis, whereas endomyocardial biopsy and genetics are used for confirmation of the underlying diagnosis. Interdisciplinary teams including hemato-oncology, neurology, nephrology in addition to cardiology are essential to enable personalized targeted treatment strategies.

κ and λ urine free light chains: a new method for quantification

Immunofixation electrophoresis of urinary proteins, coupled with densitometric analysis, is the gold standard method for determining urinary monoclonal free light chains (FLCs), i.e. Bence Jones protein. Recently, immunochemical methods have been developed for Bence Jones protein quantification, but no such method has been widely adopted. This study evaluated a new antibody-based immunoturbidimetry method for urinary FLC quantification, using immunofixation electrophoresis as reference. κ and λ FLCs were measured in urine specimens from 95 (training cohort) and 103 (testing cohort) patients by both immunofixation electrophoresis and immunoturbidimetry. There was almost perfect concordance in the training cohort between the new immunoturbidimetry assay and immunofixation electrophoresis and substantial agreement, with Cohen kappa of 0.85 and 0.75, for κ and λ FLC determination, respectively. Results were confirmed in the testing cohort, where Cohen kappa was 0.86 for κ and 0.94 for λ FLCs. The κ FLC assay had 88% sensitivity and 98%-100% specificity; the λ FLC assay had 94% and 96% sensitivity and 91% and 99% specificity in the training and testing cohorts, respectively. The new immunochemical method has a satisfactory performance and almost perfect agreement with immunofixation electrophoresis and gives the advantage of FLC quantification.

Free Light Chains as a Novel Diagnostic Biomarker of Immune System Abnormalities in Multiple Sclerosis and HIV Infection.

Introduction Immunoglobulins are molecules composed of two heavy and two light chains. Light chains are produced by B lymphocytes during the synthesis of immunoglobulins, and physiologically light chains are generally produced in excess compared to heavy chains. Light chains that are not combined to heavy chains in a whole immunoglobulin are called free light chains (FLCs). B-cell abnormalities are associated with disorders leading to an abnormal concentration of free light chains. In this study, we focus on the described changes of serum and cerebrospinal fluid concentration of free light chains in inflammatory disorders: multiple sclerosis, HIV infection, and HIV-associated lymphomas. Methods We performed broad research of the literature pertaining to our investigation via the MEDLINE/PubMed database. Results It has been proven that FLC determination can provide rapid information about intrathecal inflammation in patients with multiple sclerosis. Moreover, literature data suggest that free light chain determination is the most interesting alternative for oligoclonal band analysis. In the present review, we also described that HIV-related immune system dysfunction is associated with an elevated concentration of serum-free light chains. Additionally, FLCs are potentially a strong and sensitive predictor of the risk of developing HIV-associated lymphomas. Conclusion Based on these published findings, we suggest that free light chains have high diagnostic sensitivity, which probably enables application in laboratory diagnostics.

Determination of serum free light chains as a marker of systemic lupus flare.

The aim of this study was to explore the usefulness of the determination of free light chains (FLC) in serum as a biomarker of flare in patients with systemic lupus erythematosus (SLE) and to analyze the differences in their discriminatory capacity with complement C3 and C4. This was a prospective cohort study. The definition of flare was based on the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) Flare Index. The discriminatory capacity of FLC and C3 and C4 levels was compared using receiver operating characteristic (ROC) curves and the area under the curve (AUC). Forty-six patients were enrolled. Patients with SLE flare showed significantly lower C3 (p = 0.025) and C4 levels (p = 0.028), as well as a higher concentration of lambda light chains (λ-LC) (p = 0.028) compared with the non-flare group. λ-LC, as opposed to kappa light chains and total light chains, demonstrated a discriminatory capacity for detecting the presence of SLE flare (AUC 0.781), with 100% sensitivity, 65% specificity, and 69.6% of patients correctly classified for a cutoff point of ≥ 19.5 mg/L. Complement C3 and C4 also showed a high discriminatory capacity for SLE flare (AUC 0.804 and 0.837, respectively). Comparing λ-LC, C3, and C4, the last one demonstrates better discriminatory capacity for SLE flare with the highest AUC (0.837; 95% CI 0.663-1.000). λ-LC have good discriminatory capacity for SLE flare and could be useful as a biomarker of SLE exacerbation.Key Points• The usefulness of free light chains as a biomarker could be compared with complement.• Lambda free light chains have good discriminatory capacity for SLE flare.• Free light chains are a promising marker of SLE activity.

Comparison of three different assays demonstrates heterogeneity in determination of serum free light chains - implications on diagnostic and therapeutic monitoring of multiple myeloma

Determination of serum free light chains (FLC) is established as standard for diagnosis and monitoring of multiple myeloma (MM) and other plasma cell dyscrasias. In 2014, the revised IMWG criteria implemented the serum free light chain ratio of involved FLC (iFLC) / non-involved FLC (niFLC) > 100 as a biomarker defining MM requiring treatment. This recommendation was based on Freelite assay, which relies on polyclonal antisera. Additionally, the monoclonal N-Latex FLC assay and more recently, the polyclonal Sebia FLC assay are available and approved for determination of FLC.

Comparative study of methods for the determination of free light chains (FLC) in 24-hour urine

Cerebrospinal fluid (CSF) biomarkers are valuable tools for the diagnosis of neurological diseases. We aimed to investigate within a retrospective multicentric study the final diagnosis associated with very high CSF Tau levels and to identify patterns of biomarkers that would differentiate them in clinical practice, to help clinical biologists into physicians' counseling.Within the national multicentric network ePLM, we included 1743 patients from January 1, 2008, to December 31, 2013, with CSF biomarkers assayed by the same Innotest assays (protein Tau, phospho-Tau [pTau], and Aβ 1-42). We identified 205 patients with protein Tau concentration higher than 1200 pg/mL and final diagnosis.Among those patients, 105 (51.2%) were suffering from Alzheimer's disease, 37 (18%) from sporadic Creuztfeldt-Jakob disease, and 63 (30.7%) from other neurological diseases including paraneoplastic/ central nervous system tumor, frontotemporal dementia, other diagnoses, amyloid angiopathy, Lewy body dementia, and infections of the central nervous system. Phospho-Tau, Aβ1-42 and Aβ1-42/pTau values differed significantly between the three groups of patients (p < .001). An Aβ1-42/pTau ratio between 4.7 and 9.7 was suggestive of other neurological diseases (threshold in AD: 8.3). CSF 14-3-3 was useful to discriminate Alzheimer's disease from Creuztfeldt-Jakob disease in case of Aβ1-42 concentrations <550 pg/mL or pTau>60 pg/mL.This work emphasizes the interest of a well-thought-out interpretation of CSF biomarkers in neurological diseases, particularly in the case of high Tau protein concentrations in the CSF.

Cerebrospinal fluid free light chains determination in oligoclonal bands negative patients with suspected multiple sclerosis

Cerebrospinal fluid free light chains determination in oligoclonal bands negative patients with suspected multiple sclerosis

Modern approaches to the detection of monoclonal gammopathy of undetermined significance (MGUS) in patients with kidney diseases

To assess the diagnostic value of "Freelite" methods in addition to electrophoresis (EF) and immunofixation (IF) of serum and urine proteins for detecting MG in patients with kidney diseases. 87 patients with kidney damage, in which MG was established using the method of electrophoresis of serum proteins (EF), immunofixation (IF) and the method of free light chains determination - FLC "Freelite" were selected. The diagnostic value of three - component serum panel was compared with EF and IF. AL-amyloidosis with kidney involvement was diagnosed in 41% patients, cryoglobulinemic glomerulonephritis (cryo GN) - in 18%, chronic glomerulonephritis (CGN) - in 35%, also there was small number of patients with light chain disease and cast - nephropathy. Determination of MG using EP was possible only in 38 (44%). Adding to the serum electrophoretic methods instead of the "Freelite" method, the urine EF and IF reduced the number of missed patients with monoclonal gammopathy from 24 (27%) to 11 (13%), including in the subgroup of patients with AL-amyloidosis but did not reach the sensitivity of the three - component serum screening panel. In 10 (11.5%) MG was represented only by intact mIg with one type of light chain, either κ or λ. Most often - in 25% of patients, intact monoclonal gammopathy was observed in HCV (+) cryo GN. A combination of intact mIgM, mIgG or mIgA with mFLC, was detected in 37 (42.5%). In almost half (46%) of the patients, only mFLC was detected - an abnormal κ/λ ratio. The serum screening panel EF + IF + "Freelite" spreads the low - grade monoclonal gammopathy recognition (MGUS) and should be included in the algorithm of examining patients with kidney disease.

Effects of Long-Term Storage on Serum Free Light Chain Stability

Determination and quantification of serum free light chains (FLC) is essential for the diagnosis and monitoring of patients with monoclonal gammopathies. Currently, the Freelite assay (The Binding Site, United Kingdom) and the N Latex FLC assay (Siemens Healthineers, Germany) are available for FLC determination. Data concerning stability of FLC following long-term storage are limited. Therefore, the aim of the present study is to investigate the stability of FLC in frozen samples determined by the N latex FLC assay. One hundred eighty-eight serum samples from 47 patients with monoclonal gammopathies were analyzed at the beginning and after long-term storage (-20°C, 193 - 568 days). Serum free light chain kappa (κFLC) and lambda (λFLC) concentrations were measured, and the corresponding kappa/lambda (κ/λ FLC) ratios were calculated. All samples were analyzed with the N latex FLC assay on a single BNII System. Comparison analyses between fresh and stored samples revealed very strong correlations for the determination of κFLC (r = 0.993), λFLC (r = 0.998) and the calculated κ/λ FLC ratio (r = 0.997). Median percentage changes of κFLC (-0.5%) and λFLC (-0.8%) measurements and the calculated κ/λ FLC ratios (-3.7%) were within the calculated analytical imprecision of the FLC assay. Changes of κFLC (r = 0.17, p = 0.02) and λFLC (r = 0.28, p < 0.01) concentrations and of the κ/λ FLC ratio (r = 0.18, p = 0.01) over time were very weak, but statistically significant. Serum free light chains in serum samples are sufficiently stable following long-term frozen storage and are therefore suitable to be measured with the N Latex FLC assay.

Determination of kFLC and K Index in cerebrospinal fluid: A valid alternative to assessintrathecal immunoglobulin synthesis

Intrathecal immunoglobulin synthesis is observed in several disorders of the central nervous system, but its detection by current laboratory tests is relatively insensitive and operator depending. We assessed the diagnostic accuracy of a nephelometric assay for k free light chain determination in cerebrospinal fluid and serum. The patients were grouped according to clinical and laboratory criteria. ROC curves for all methods were performed to find the best cut-off value. kFLC Index seems to be more accurate than other parameters. Our data indicate that nephelometric assay for kFLCs in CSF reliably detect intrathecal immunoglobulin synthesis and discriminate multiple sclerosis patients.