Free Light Chain Measurements Research Articles

Primary Data on ATTR-Amyloidosis Prevalence Among Elderly Patients With Left Ventricular Hypertrophy in Russia.

To estimate the prevalence of amyloid cardiomyopathy (CM) caused by transthyretin amyloidosis (ATTR) and immunoglobulin light chain (AL) amyloidosis among patients aged >65 years with interventricular septal (IVS) hypertrophy of ≥14 mm. From January through August 2023, 60 patients (mean age 7.2±7.3 years, 34 (56.67%) men) were enrolled. Patients meeting the inclusion criteria underwent an echocardiographic study with determining the myocardial longitudinal strain, myocardial scintigraphy with 99mTc-pyrfotech, myocardial single-photon emission computed tomography, measurement of N-terminal fragment of brain natriuretic peptide and troponin I, and the immunochemical study of serum and urine proteins with measurement of free light chains. In the presence of grades 2 and 3 radiopharmaceutical uptake according to scintigraphy, a molecular genetic study was performed for differential diagnosis of wild-type transthyretin amyloidosis (wtATTR) and hereditary/variant (hATTR) ATTR-CM. According to data of myocardial scintigraphy with 99mTc-pyrfotech, grade 3 uptake in the absence of monoclonal secretion was detected in 5 (8.3%) cases and grade 2 radiotracer uptake in the absence of monoclonal secretion was detected in 6 (10%) patients. Myeloma complicated by AL amyloidosis and primary AL amyloidosis were found in 5 (8.3%) patients. Among patients aged ≥65 years with IVS hypertrophy ≥14 mm, amyloid CM was detected in 20% of cases (12 patients), including 5 cases (8.3%) of AL amyloidosis and 7 cases (11.7%) of ATTR amyloidosis.

Serum Free Light Chain Kinetics Is Predictive of Renal Response in Myeloma Patients With Renal Impairment—An ALLG Trial of Carfilzomib-Dexamethasone Therapy in Frontline and Relapse

Background and PurposeRenal impairment (RI) confers adverse prognosis in myeloma; its reversal and avoidance of dialysis are crucial. We investigated whether serum free light chain (SFLC) measurements can predict renal outcome, to enable change in therapy to optimize prognosis and avoid dialysis. Patients and MethodsWe investigated 36 myeloma patients (17 newly diagnosed [ND]; 19 relapsed refractory [RR]; with median of 5 prior lines) with eGFR 15-40 ml/min treated with carfilzomib (Cfz)-dexamethasone to determine whether SFLC kinetics can predict renal outcomes, and assess efficacy and tolerability. ResultsThe change in involved SFLC at Cycle 2 Day 1 was significantly correlated with renal function; for every one log10 reduction in involved SFLC, eGFR increased by 9.0-15.0 mL/min at cycles 2-4, with SFLC reduction of 54%-78%. At a median follow-up of 30.6 months, renal outcomes were favorable—CRrenal 25%, MRrenal 36%. Disease responses (ND 100%, RR 75%), progression-free survival (ND 32.2 months, RR 11.1 months) and overall survival (ND not reached, RR 42.0 months) were comparable to patients without RI. There was significant toxicity, including Cfz-related cardiac impairment of 20% within a cohort with high co-morbidity, and a high incidence of infections. ConclusionWe propose that one log10 reduction in involved SFLC at Cycle 2 Day 1 is an appropriate target for reducing the risk of dialysis in myeloma patients with RI; below this threshold patients may benefit from a change in therapy. While Cfz-dexamethasone achieved favorable renal and disease outcomes, toxicity can be significant in this vulnerable cohort.

Urine Immunofixation Electrophoresis for Diagnosis of Monoclonal Gammopathy: Evaluation of Methods for Urine Concentration.

Examination of urine by immunofixation electrophoresis (UIFE) is one of the tests recommended for screening and monitoring of monoclonal gammopathies, especially multiple myeloma. Unlike the serum free light chain measurement, a positive result on urine immunofixation is diagnostic for monoclonal immunoglobulin light chains. Urine is usually concentrated, generally by membrane filtration, prior to electrophoresis. Alternative methods to membrane filtration for urine concentration were examined. Residual urine specimens submitted for urine protein electrophoresis were concentrated by precipitation of the proteins by ammonium sulfate salt precipitation, precipitation with ethanol and acetonitrile, and by desiccation. The concentrated specimens were subjected to immunofixation electrophoresis using antisera to free light chains (FLC). The results were compared with those from conventional immunofixation electrophoresis using specimens concentrated by membrane filtration. Ammonium sulfate, ethanol, and acetonitrile precipitation results were less than satisfactory. Concentration by desiccation provided results comparable, if not better than, those by membrane filtration and conventional UIFE. The cost of desiccation is minimal compared to more than $5.00/specimen cost of concentration by membrane filtration. The differences in the results with conventional UIFE and the method described here are likely due to (a) variability in the reactivity of different antisera to free monoclonal light chains, and (b) obscuration of monoclonal free light chains by co-migration with intact immunoglobulin monoclonal proteins. Concentrating urine by desiccation for immunofixation electrophoresis is technically simple, inexpensive, and provides results comparable to concentrating by membrane filtration. Using FLC provides a more sensitive assay than using conventional antisera.

Comparison of two free light chain assays: performance of the free light chain ratio as risk factor for MGUS progression

Abstract Monoclonal gammopathy of undetermined significance (MGUS) is the most common plasma cell dyscrasia, present in ~3% of the population over 50yo. MGUS carries a 1% per year risk of malignant transformation for the rest of the affected individual’s life; long-term followup is recommended for all patients with MGUS. Different risk stratification models exist to evaluate potential for progression to malignancy. The Mayo risk model, published in 2005, uses the presence of 3 risk factors (abnormal free light chain (FLC) kappa/lambda ratio (KLr), M-spike ≥1.5 g/dL, non-IgG isotype) to confer a 3% per year risk of progression instead of the average 1%. For many years, the only FDA-approved measurement of FLC was the FreeLite assay (Binding Site), which uses polyclonal sheep antibodies. Recently, other FLC assays have become available in the US, including the Sebia FLC ELISA, which employs rabbit polyclonal antibodies. The assays have similar reference intervals (RI), however differences in analytical performance between the FreeLite and Sebia were previously reported. The objective of this study was to determine the performance of the Sebia FLC assay in the Mayo risk stratification model of MGUS patients for progression in comparison to FreeLite. Cryopreserved serum samples from a cohort of 923 MGUS patients with available long-term clinical followup (median follow-up time: 7.7years, range: 0.0 to 46.9) was used to measure FLC using Sebia ELISA on a DS2 automated platform (Dynex) and FreeLite on a Siemens BNII nephelometer. Passing-Bablok (P-B) regression and Spearman correlation were used to compare the KLr between assays. Cox proportional hazards models for progression to multiple myeloma or a related plasma cell malignancy were used to estimate the prognostic effect and ability to discriminate low and high risk of abnormal KLr for each assay. Analyses were carried out in R software. Correlation between Sebia and FreeLite KLr had a Spearman r = 0.796; P-B fit: Sebia KLr = 0.825*(FreeLite KLr) – 0.048, 95% CI of slope: 0.810-0.839). With FreeLite, 32.9% of patients had a KLr outside RI for the method. For Sebia, 48.0% of patients had a KLr outside the method specific RI. Despite the individual samples analytical disagreement, both assays showed similar clinical performance for risk stratification: Sebia abnormal KLr was associated with a hazard ratio (HR) of 2.77 (95%CI: 1.79-4.28 c-statistic=0.6505) for progression, while FreeLite abnormal KLr was associated with a HR of 3.31 (95%CI: 2.20-5.00, c-statistic=0.6529), and the difference in c-statistics was not statistically significant (p=0.93). The risk assessment is performed only once per patient, at the initial diagnosis of MGUS. The similarity in clinical performance between FreeLite and Sebia assays support the use of either method as a predictor for risk of progression for MGUS patients.

Non-Invasive MRD Monitoring in Multiple Myeloma Patients By Heavy/Light Chain Analysis

Introduction The majority of multiple myeloma (MM) patients are now achieving very deep responses. The most sensitive disease detection techniques are currently bone marrow assays. However, as bone marrow sampling is invasive and unpleasant for patients it is important to investigate whether blood-based assays could be equally or more informative of disease status. The heavy/light chain assay (Hevylite TM, The Binding Site, UK) evaluates serum heavy/light chains (HLC) for IgG, IgA and IgM M-proteins. This study assessed whether the HLC assay could act as an effective marker for disease in the bone marrow of treated MM patients and evaluated the prognostic utility of HLC measurements at best response and relapse time points. Methods 104 IgG and IgA MM patients were recruited either prior to transplant or during chemotherapy. Median follow up was 18 months. Routine M-protein tests were performed alongside HLC testing with parameters including involved HLC (iHLC), uninvolved HLC (uHLC) and kappa/lambda HLC ratio (HLCr). A bone marrow flow cytometry (NGF) assay was performed up to a sensitivity of 10 -6 and was considered to be the gold standard assay. Disease response was determined according to the IMWG criteria. Results and Discussion At pre- and post-transplant time points there was significant agreement between HLC measurements and NGF, with uHLC being the most sensitive measurement (86%) and HLCr the most specific (100%). Both uHLC and HLCr show substantial agreement with the bone marrow NGF method whilst iHLC cannot be used to indicate bone marrow status. Survival analysis showed significantly inferior progression free survival (PFS) in patients with an abnormal uHLC (p=0.01) (Figure A) or HLCr (p=0.02) result post-transplant but no survival difference based on iHLC status (p=0.78) (Figure B). Interestingly, performing survival analysis on these same samples using serum immunofixation (IFE) status (positive or negative) did not produce a significant PFS difference between participants (p=0.21). During long term follow up, HLC values showed a correlation with depth of response, with uHLC being abnormal in 60% of complete response (CR) patients. This suggests that those participants currently grouped as CR may be able to be further subdivided according to uHLC level and this could have a prognostic value in the monitoring and treatment of these patients. At best response uHLC was the only HLC or free light chain (FLC) measurement which gave a significant difference in PFS for all patients in partial response (PR) or better (p=0.005), remaining true when analysing patients in ≥CR only (p=0.002). The addition of free light chain measurements into the HLC analysis did not improve the significance of these survival differences. In relapsed patients, paired comparisons of M-protein and disease activity markers at best response vs. prior to clinical relapse were performed. uHLC was the only marker which was significantly different between the two time points in IgG and IgA patients. The significance of this was confirmed by showing that those patients in stable disease did not experience a significant change in uHLC levels. For other M-protein variables such as total immunoglobulin, IFE status and FLC values there was an increase in levels or abnormality between best response and pre-relapse but these were not significant. The paired comparison suggests that monitoring an individual using HLC could help to detect relapse earlier than conventional methods. In all analyses performed the HLC assay showed increased sensitivity and utility over the IFE technique. Conclusion This study suggests that the HLC assay can be used prior to bone marrow analysis to help influence decisions and improve the patient and laboratory experience. These results can be put into practice during patient follow up post initial treatment in the following ways: At deepest response an abnormal uHLC or HLCr suggests a positive MRD status, meaning a possible reduction or delay in the requirement for bone marrow assessment.All patients in ≥VGPR should have HLC performed alongside conventional assays during follow up.If uHLC values become abnormal during follow up then it should be assumed that the patient is about to undergo relapse. The measurement of HLC values have been shown to be a significant marker in this study, for sensitively detecting the M-protein, giving further clarification of response status and predicting early relapse.

Revised Definition of Free Light Chains in Serum and Light Chain Monoclonal Gammopathy of Undetermined Significance: Results of the Istopmm Study

Background: Serum free light chain (FLC) measurement, consisting of serum free kappa, serum free lambda, and a calculated FLC ratio (kappa/lambda), plays a pivotal role in the diagnosis, risk stratification and management of plasma cell disorders. Light chain monoclonal gammopathy of undetermined significance (LC-MGUS), is defined as abnormal FLC ratio with elevation of the involved FLC without evidence of heavy chain M protein or end-organ damage attributed to the plasma cell disorder. Several years ago, reference intervals for serum kappa (3.3-19.4 mg/L) and lambda (5.7-26.3 mg/L) FLC and FLC ratio (0.26-1.65) were defined in a small retrospective cohort (N = 282) of healthy individuals. Limitation of these reference intervals include inaccurate distributions among individuals with impaired kidney function. Recently, we addressed this matter in a large population-based study focusing on individuals with estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73m 2, the results of which led to redefined reference intervals for patients with chronic kidney disease (Long et al, Blood Cancer J. 2022). Here, using a large cohort (N=41,882) of screened individuals, we aimed to determine FLC reference intervals in individuals with normal kidney function (eGFR ≥ 60 mL/min/1.73m 2). Methods: Data were collected from the ongoing Iceland Screens, Treats, or Prevents Multiple Myeloma (iStopMM) study, which focuses on population-based screening for MGUS. A total of 75,422 individuals aged ≥ 40 years (representing 51% of this age group in the Icelandic population) were screened for MGUS by serum protein electrophoresis, immunofixation, and serum FLC assay (Freelite®), and two-thirds of MGUS cases were randomized to active follow-up. Participants' eGFR was calculated using serum creatinine (CKD-EPI) closest to the time of screening. Participants with heavy chain M protein, known lymphoproliferative disorder, unknown eGFR or eGFR < 60 mL/min/1.73m 2, were excluded. The 0.5 and 99.5 percentiles of kappa FLC, lambda FLC, and the FLC ratio distributions were assessed for the whole group, and subgroups of age, sex, and different levels of eGFR. A nonparametric bootstrapping method was used to calculate the 95% confidence intervals. Partitioning was determined based on the proportion of subgroups (age, sex and eGFR) outside the whole group reference interval. Results: After application of the exclusion criteria, 41,882 participants were included for further analysis. The median (interquartile range, IQR) serum free kappa was 14.3 (11.6-17.8) mg/L, serum free lambda 14.2 (11.6-17.5) mg/L, and the FLC ratio was 1.02 (0.85-1.21). The median (IQR) age was 60 (52-68) years, eGFR 84 (74-94) mL/min/1.73 m 2, and 43% were male. A strong correlation was found between age and serum kappa FLC (ρ = 0.27, p < 0.001), lambda FLC (ρ = 0.14, p < 0.001), and the FLC ratio (ρ = 0.16, p < 0.001). Use of standard reference intervals yielded abnormal results for 17.5%, 3.9%, and 4.5% of serum kappa, lambda, and FLC ratio determinations, respectively, and a prevalence of LC-MGUS of 2.0% (96% kappa and 4% lambda). Based on these findings, we established new reference intervals for serum kappa and lambda FLC and FLC ratio, partitioned by age < 70 years and ≥ 70 years (Table). Utilizing the new reference intervals the crude prevalence of LC-MGUS was 0.3% (54% kappa and 46% lambda), yielding a relative decrease of 83%. Among the group of individuals diagnosed with LC-MGUS based on standard reference intervals who did not meet the diagnostic criteria using our revised reference intervals - none had progressed to a lymphoproliferative disorder after a median follow-up time of 42 months. Conclusion: Based on prospective screening of more than 40,000 individuals and after 3.5 years of follow-up, we show that standard reference intervals for serum FLC and FLC ratio appear inaccurate for persons with preserved kidney function. We propose a revision of the reference intervals for serum FLC and FLC ratio, and a new definition of LC MGUS (Figure). Implementation of new reference intervals will decrease the rate of false positive diagnosis of LC-MGUS in individuals with preserved kidney function by more than 80%. This, in turn, will reduce the unnecessary psychological and financial burden driven by clinical evaluation and lifelong monitoring of these individuals.

B-179 Development of a Reflex Mass Spectrometric Workflow for Confirmation of IgE and IgD Specificity Paraproteins Utilising the EXENT® Platform

Abstract Background The EXENT® (GAM) assay is a MALDI-TOF (Matrix Assisted Laser Desorption Ionisation Time of Flight) mass spectrometry-based solution which utilises IgG, IgA, IgM, total kappa and total lambda specific paramagnetic beads, which could be used in the investigation of monoclonal proteins in multiple myeloma and other plasma cell disorders (in development by The Binding Site (TBS), part of Thermo Fisher Scientific). Rare cases of IgD and IgE myelomas will be partially typed with the current iteration of the EXENT (GAM) assay. We present here a workflow to confirm the heavy chain specificity of such paraproteins as IgD or IgE using reflex LC-MS analysis of EXENT eluates. Methods Samples known to contain IgD (2) or IgE (3) paraproteins were provided from either routine workload at the immunology laboratory at Birmingham Heartlands Hospital, UK or an internal library of historical myeloma samples. Capillary zone electrophoresis (CZE) and immunofixation (IFE) were performed on Capillarys2™ and Hydrasys2 Scan™ platforms, respectively (Sebia, France). Serum free light chain (sFLC) measurement was performed using Freelite® reagents (The Binding Site, UK) on a Cobas c501 turbidimeter (Roche, Switzerland). Samples were prepared via EXENT (GAM) assay, by separately incubating diluted serum with antisera specific for IgG, IgA, IgM, total kappa and total lambda conjugated to paramagnetic beads. After washes, purified immunoglobulins were treated to reduce and elute the light chain component. Samples were mixed with matrix, spotted onto a MALDI target plate and acquired by MALDI-TOF MS. Once light-chain specificity of the suspected IgD or IgE paraprotein was determined, repeat immuno-precipitation with the same light-chain bead was carried out. Eluted samples were neutralised, transferred to fresh tubes, reduced, alkylated and digested with trypsin for 3 h. After acidification digested samples were analysed by C18 reverse phase UPLC on a BioAccord LC-MS system (Waters, UK). Data was then screened against a database of known immunoglobulin heavy chain peptides to assess the presence of heavy chain peptides specific for each immunoglobulin isotype. Results In each sample tested, the EXENT solution identified at least one monoclonal light chain that was only seen in the total kappa or total lambda immunoprecipitations with no corresponding monoclonal peak(s) at the same mass(es) in the IgG, IgA or IgM specificities. This finding would be consistent with the presence of clonal plasma cells producing either monoclonal free light chains only, or IgD and IgE paraproteins. Subsequent LC-MS and LC-MSe (tandem MS) analysis of reduced, alkylated and tryptically digested eluates corresponding to these suspected IgD and IgE samples produced high quality peptide sequencing data. The data identified multiple IgD or IgE specific peptides in each sample and showed between 40% and 66% sequence coverage for IgD or IgE heavy-chain constant regions. Thus, confirming the presence of IgD or IgE in these samples which had been partially typed by the EXENT solution. Conclusion This data demonstrates that the EXENT (GAM) assay could potentially aid in detection of IgD and IgE paraproteins when combined with LC-MS proteomic techniques, as it allows efficient and facile confirmation of these rare heavy chain isotypes.

Freelite and Kloneus assays in free light chain measurements in patients with renal impairment

BackgroundSerum free light chain (FLC) quantification is a diagnostic criterion for monoclonal gammopathy and its values in patients with renal impairment are different from those in healthy subjects. The aim of this study was to evaluate Freelite and Kloneus assays in these patients. MethodsIn this retrospective study, serum samples from 226 patients with chronic kidney disease (CKD) of stages 2–5 were measured with a Freelite assay on the Optilite system and with a Kloneus assay on the AU5800 system and compared with controls without renal impairment. ResultsBoth kappa FLC (K-FLC) and lambda FLC (L-FLC) concentrations increased with Kloneus and Freelite assays with each increment in CKD stage. In patients with CKD, Kloneus detected lower concentrations of K-FLC (median: 20.4 mg/L; 95% range: 9.8–57.2) than Freelite (median: 36.5 mg/L; 95% range: 16.5–137.7) and higher concentrations of L-FLC (median: 32.2 mg/L; 95% range: 14.4–96.7) than Freelite (median: 25.4 mg/L; 95% range: 11.9–86.0). This resulted in significantly different kappa/lambda ratios (K/L-FLC) in patients with CKD for the two tests. The Freelite K/L-FLC in the CKD group (median: 1.50; min–max: 0.66–3.45) was significantly increased compared with healthy controls, and the Kloneus K/L-FLC in the CKD group (median: 0.63; 95 % min–max: 0.34–1.01) was slightly lower. ConclusionsThese findings demonstrate that Freelite and Kloneus assays provide higher but not parallel values when FLCs are measured in patients with CKD, so an increase in K/L-FLC was observed in the case of Freelite, and we found a slight decrease in the case of Kloneus.

#5831 LIGHT CHAIN REMOVAL IN MULTIPLE MYELOMA PATIENTS WITH HFR-SUPRA HEMODIALYSIS: OUR EXPERIENCE

Abstract Background and Aims Kidney injury is a common complication in multiple myeloma (MM) and it has a negative prognostic implication. Most common cause of Acute Kidney Injury (AKI) in these patients is Light chain Cast Nephropathy, where free light chains precipitate in the tubules and bind with uromodulin, turning into intratubular casts that obstruct the tubules and also promote local giant cell reaction and interstitial inflammation and fibrosis. Free light chains (FLCs) can also damage the kidneys due to direct tubular toxicity when excessive amounts are reabsorbed by the proximal tubules. Targeted therapy to reduce FLC load can help recover renal function. Both total reduction and reduction speed are relevant for prognosis. FLC removal through extracorporeal techniques can be used as an adjuvant therapy, having an important part on the evolution of the disease. We gathered data from our experience treating MM patients with AKI with HFR-supra hemodialysis (HD) and analized the evolution and possible influence of this technique on renal recovery. Method This is an observational retrospective study. We included all patients with a diagnosis of multiple myeloma and acute kidney injury who received HFR-Supra hemodialysis in between years 2016-2022 in Hospital Virgen Macarena (Seville). We initially performed 6-10 daily HFR-Supra HD sessions and then modulated the frequency based on renal response (if renal replacement therapy had to be continued they underwent a usual hemodialysis regime 3 days a week). We continued these sessions until renal recovery was achieved or free light chain levels were reduced in agreement with the Hematology team. Measurement of pre and post dialysis FLCs was made always at first and last session and at least once in between, depending on the total number of sessions. Results 12 patients, with mean age at diagnosis 63.6 (43-86) years, presented with AKI stage KDIGO 3. 1 of them was oliguric. Median serum creatinine at diagnosis was 4.4 mg/dL [2,2-17], mean proteinuria was 4,1g/24 h [0,7-8,7] and 66,7% had positive Bence Jones proteinuria (mean 2,3g/24 h). 2 of the patients had previous chronic kidney disease stage 3a. All of them were diagnosed with Light Chain Multiple Myeloma (75% kappa, mean 10346 mg/L; 25% lambda, mean 5990 mg/L). Mean clonal bone marrow plasma cell was 20,7% [2-55]. According to the Revised International Staging System (R-ISS), 25% were stage 2 and 75% were stage 3. Renal biopsy was performed in 4 patients, all showed evidence of Cast Nephropathy. The indication for starting HFR-Supra HD was FLC removal in 9 patients, need of renal replacement therapy in 1 and both in 2 patients. We have experience in our center with using this therapy as an adyuvant treatment and often we start the technique in patients who present with AKI but would not necessarily have immediate need for renal replacement therapy. The goal is to remove FLCs and avoid further damage to the kidney tissue. Out of the 12 patients, 9 were able so stop dialysis (75%). They received a mean number of 12,4 [3-41] sessions in 3,7 [0,2-25] months). Free light chain removal per session was 24% on average [5-43%]. All of them were started on bortezomib-dexamethasone regime as initial chemotherapy for MM. As per renal recovery, at 3 months 33,3% achieved complete response, 11,1% partial response and 55,6% minimal response. At 1 year, 42,9% achieved complete response, 14,3% partial response and 42,9% minimal response. One-year survival rate was 91,7% (1 patient died from respiratory sepsis less than 1 month after diagnosis). Conclusion HFR-Supra hemodialyisis achieved a 24% free light chain removal per session on average. After presenting severe AKI (KDIGO 3), almost 43% of patients who received this adyuvant therapy obtained full renal recovery at 1 year and in 75% of patients withdrawal from hemodialysis was possible. 1 year survival was 91,7%.

Free Light Chains κ and λ as New Biomarkers of Selected Diseases.

Diagnostic and prognostic markers are necessary to help in patient diagnosis and the prediction of future clinical events or disease progression. As promising biomarkers of selected diseases, the free light chains (FLCs) κ and λ were considered. Measurements of FLCs are currently used in routine diagnostics of, for example, multiple myeloma, and the usefulness of FLCs as biomarkers of monoclonal gammopathies is well understood. Therefore, this review focuses on the studies concerning FLCs as new potential biomarkers of other disorders in which an inflammatory background has been observed. We performed a bibliometric review of studies indexed in MEDLINE to assess the clinical significance of FLCs. Altered levels of FLCs were observed both in diseases strongly connected with inflammation such as viral infections, tick-borne diseases or rheumatic disorders, and disorders that are moderately associated with immune system reactions, e.g., multiple sclerosis, diabetes, cardiovascular disorders and cancers. Increased concentrations of FLCs appear to be a useful prognostic marker in patients with multiple sclerosis or tick-borne encephalitis. Intensive synthesis of FLCs may also reflect the production of specific antibodies against pathogens such as SARS-CoV-2. Moreover, abnormal FLC concentrations might predict the development of diabetic kidney disease in patients with type 2 diabetes. Markedly elevated levels are also associated with increased risk of hospitalization and death in patients with cardiovascular disorders. Additionally, FLCs have been found to be increased in rheumatic diseases and have been related to disease activity. Furthermore, it has been suggested that inhibition of FLCs would reduce the progression of tumorigenesis in breast cancer or colitis-associated colon carcinogenesis. In conclusion, abnormal levels of κ and λ FLCs, as well as the ratio of κ:λ, are usually the result of disturbances in the synthesis of immunoglobulins as an effect of overactive inflammatory reactions. Therefore, it seems that κ and λ FLCs may be significant diagnostic and prognostic biomarkers of selected diseases. Moreover, the inhibition of FLCs appears to be a promising therapeutical target for the treatment of various disorders where inflammation plays an important role in the development or progression of the disease.

Liquid biopsy-based monitoring of residual disease in multiple myeloma by analysis of the rearranged immunoglobulin genes-A feasibility study.

The need for sensitive monitoring of minimal/measurable residual disease (MRD) in multiple myeloma emerged as novel therapies led to deeper responses. Moreover, the potential benefits of blood-based analyses, the so-called liquid biopsy is prompting more and more studies to assess its feasibility. Considering these recent demands, we aimed to optimize a highly sensitive molecular system based on the rearranged immunoglobulin (Ig) genes to monitor MRD from peripheral blood. We analyzed a small group of myeloma patients with the high-risk t(4;14) translocation, using next-generation sequencing of Ig genes and droplet digital PCR of patient-specific Ig heavy chain (IgH) sequences. Moreover, well established monitoring methods such as multiparametric flow cytometry and RT-qPCR of the fusion transcript IgH::MMSET (IgH and multiple myeloma SET domain-containing protein) were utilized to evaluate the feasibility of these novel molecular tools. Serum measurements of M-protein and free light chains together with the clinical assessment by the treating physician served as routine clinical data. We found significant correlation between our molecular data and clinical parameters, using Spearman correlations. While the comparisons of the Ig-based methods and the other monitoring methods (flow cytometry, qPCR) were not statistically evaluable, we found common trends in their target detection. Regarding longitudinal disease monitoring, the applied methods yielded complementary information thus increasing the reliability of MRD evaluation. We also detected indications of early relapse before clinical signs, although this implication needs further verification in a larger patient cohort.

The Clinical Significance of Serum Free Light Chains in Bladder Cancer.

This research aimed to assess the clinical usefulness of serum kappa (κ) and lambda (λ) free light chains (FLCs) in patients with bladder cancer (BC). One hundred samples were collected and analysed from healthy volunteers (C) and bladder cancer patients. Cancer patients were divided into two subgroups: low-grade (LG) and high-grade cancer (HG). Concentrations of FLCs, CEA, CA19-9, creatinine and urea were measured per manufacturers' guidelines. The concentrations of κ and λ FLCs and CEA were significantly higher in BC patients in comparison to the control group. Moreover, the concentrations of κ and λ FLCs and CEA were significantly higher in both low-grade as well as high-grade cancer in comparison to the controls. The levels of κ and λ FLCs differed between tumour grades, with patients presenting higher concentrations in high-grade compared to low-grade cancer. In the total study group, κFLC correlated with λFLC, the κ:λ ratio, CRP, CEA, CA19-9, creatinine and urea. There was also a correlation between λFLC and κFLC, CRP, CEA, creatinine and urea. The λFLC showed a higher ability (sensitivity and PPV) to detect bladder cancer in comparison to κFLC and CEA. In addition, λFLC had a higher ability to exclude BC (specificity and NPV) than κFLC and CEA. λFLC also showed the highest accuracy in the detection of bladder cancer. In conclusion, the revealed differences in the concentrations of both κ and λ FLCs suggest their potential participation in bladder cancer development. Increased concentrations of free light chains in bladder cancer patients and the association with the tumour grade suggest that κ and λ FLC measurements may be useful in the diagnosis and prognosis of bladder cancer. This is the first research that evaluates the concentration of FLCs in bladder cancer, so further studies are necessary to confirm their usefulness as tumour markers of this malignancy.

Free light chains as a reliable biomarker of intrathecal synthesis in the diagnosis of CNS inflammatory diseases

ObjectiveTo address the diagnostic performances of cerebrospinal fluid (CSF) free light chains (FLC) measurements compared to oligoclonal bands (OCB) to support multiple sclerosis (MS) diagnosis. ResultskFLC index showed the highest diagnostic accuracy to detect MS patients with the highest AUC compared to OCB, IgG index, IF kFLC R, kFLC H, λFLC index and IF λFLC. ConclusionsFLC indices are biomarkers of intrathecal Immunoglobulin synthesis and central nervous system (CNS) inflammation. kFLC index can discriminate between MS and other CNS inflammatory disorders, while λFLC index is less informative for MS but can play a role to support the diagnosis of other inflammatory CNS disorders.

Rapid detection of serum free light chains by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

Introduction: Serum free light chain (FLC) measurements are increasingly prominent for patients with plasma cell disorders (PCDs) in screening, prognostic stratification, and monitoring therapy responses. Objectives: We aimed to develop a sensitive, reliable, and accurate method for diagnosing PCDs that can notably decrease the time and cost of current methods. Methods: Here, we present a novel approach for FLC measurement using immunoenrichment on micro-affinity chromatography in combination with matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) detection. In this study, serum free kappa (κ) and free lambda (λ) light chain (LC) levels in the serum of 105 patients were compared between the nephelometric serum FLC quantification and MALDI-TOF MS detection. Results: Cohen's kappa coefficient between the MALDI-TOF MS-based method and the FLC assay revealed an almost perfect agreement in the case of normal (negative) results (κ = 0.92; 95% confidence interval (CI): 0.837 to 0.968) and a good agreement in the case of increased (positive) results (κ = 0.76; 95% CI: 0.608 to 0.870). In Spearman's correlation analysis, the best correlation was found between serum free κ/λ ratios (r = 0.628, 0.496 to 0.732; p <0.0001). Our method showed sensitivity (92.5%) and specificity (76.3%) for discrimination between the κ/λ FLC ratio compared to the serum FLC assay. Conclusion: The proposed method can significantly contribute to diagnosing and monitoring PCDs as it can significantly be time-saving, cost-effective in FLC measurement.

Simultaneous Evaluation of Serum Immunofixation Electrophoresis and Serum Free Light Chain Measurements Used in the Diagnosis of Monoclonal Gammopathy and Smoldering Multiple Myeloma of Uncertain Significance in the Presence of Risk Factors

Simultaneous Evaluation of Serum Immunofixation Electrophoresis and Serum Free Light Chain Measurements Used in the Diagnosis of Monoclonal Gammopathy and Smoldering Multiple Myeloma of Uncertain Significance in the Presence of Risk Factors

591 SEQUENCE OF DIAGNOSTIC TESTING IN CARDIAC AMYLOIDOSIS: EARLY MONOCLONAL PROTEIN STUDY IS ASSOCIATED WITH BETTER OUTCOMES IN AL AMYLOIDOSIS

Abstract Background Isolated cardiac amyloidosis (CA) is a complex diagnostic scenario, highlighting the need for physician awareness in differential diagnosis. Among the different types of amyloidosis, nearly all cases of CA are caused by light chain (AL) and transthyretin amyloidosis (ATTR). Patients with suspect CA without monoclonal components (MC) in both serum and urine and normal free light chain (FLC) ratio can have a non-biopsy diagnosis of ATTR amyloidosis with bone scintigraphy (1). However, in all suspected CA with a MC (approximately 20% of patients with ATTR amyloidosis), amyloid typing is mandatory. Thus, the diagnostic pathway of CA diverges based on MC-studies. We aim to assess if different sequence of diagnostic tests can affect outcomes in patients with cardiac AL amyloidosis. Methods Pavia Amyloidosis prospectively maintained database was searched for patients with isolated cardiac AL amyloidosis referred to our Centre from January 2016 to December 2020. Patients with a known monoclonal gammopathy (MG) and with multiple organ involvement were excluded. We searched for the date of symptom onset and first suspect of CA (i.e. recognition of clinical, imaging or laboratory signs of CA). In addition, we recorded the date of the different diagnostic tests performed: i.e. echocardiogram; serum and urine immunofixation and FLC measurement (MC-study); bone scintigraphy and cardiac magnetic resonance (defined as advanced cardiac imaging). We calculated the interval between those time-points and the final diagnosis: (a) from symptom onset to diagnosis, (b) from first suspect to final diagnosis, (c) from first suspect to MC-study and (d) to advanced cardiac imaging tests. We then searched for possible intervals of time amongst those, that were able to predict death at 3 months, by means of a ROC analysis. Results A total of 94 patients were included in the analysis (25% of all patients with cardiac AL amyloidosis diagnosed in the study period). Six (6%) patients died &amp;lt;1 month from diagnosis, and 27 (29%) died &amp;lt;3 months. Median overall survival (OS) of the whole cohort was 8 months, and the median follow-up of living patients was 39 months (range 16-73). The median time from symptom onset to diagnosis was 9 months (range 1-44) and the median time from the first suspect to diagnosis was 2 months (range 0-9). An interval from the first suspect to MC-study ≥6 weeks was the only predictor of death at 3 months. None of the other tested periods were associated with a significant ability to predict survival. A delay in MC-study ≥6 weeks identified patients with more advanced cardiac stage (50% vs. 25% were stage IIIb, P=0.02) and was associated with a significantly worse outcome (median survival 13 months vs. 4 months, P=0.012). In the whole cohort, a total of 76 (81%) patients underwent at least one advanced imaging examination. Amongst those, 37 (49%) performed the imaging tests before MC-study with a higher percentage of patients who had a delay in MC-studies evaluation (69% vs. 27%; P&amp;lt;0.001). Conclusion In patients who present with isolated cardiac AL amyloidosis with previously unknown MG, a relatively short delay in identifying the amyloid MC results in a considerable reduction of survival. A delay in MC-study was associated with more advanced cardiac stage. MC studies should be the first step in the work-up of patients with suspected CA to guide biopsy vs. non-biopsy diagnostic approach.

Can urine studies be replaced by serum free light chains measurements to assign responses in multiple myeloma patients?

Serum and urine protein electrophoresis and immunofixation are the preferred techniques for monitoring monoclonal proteins and evaluating treatment response in multiple myeloma (MM) patients with measurable disease. However, urine studies are subjected to limitations that may lead to inaccuracies or prevent guidelines compliance. We retrospectively studied if the substitution of urine studies by measuring serum free light chains (sFLCs) results in a comparable disease monitoring, both in intact immunoglobulin (II) and light chain (LC) MM patients. In our cohort, equal or higher percentages of disease were identified by sFLCs at baseline and maximum response as compared to urine studies. Achieving very good partial response or better (≥VGPR) according to the response criteria proposed by the French group (evaluating sFLCs instead of urine) and the IMWG response criteria were associated to a 62% and 63% reduced risk of progression, respectively. A similar prognostic value for reaching ≥VGPR was also observed among LCMM patients when the French group and the IMWG response criteria were applied. Overall, these results support the replacement of urine studies by the sFLCs assay in IIMM. In LCMM, sFLCs could be used for monitoring and urine studies could be performed only to confirm complete remissions and progressions.

Monoclonal Gammopathy of Undetermined Significance and Risk of Chronic Kidney Disease: Results of the Population-Based Iceland Screens, Treats, or Prevents Multiple Myeloma (iStopMM) Study

Background: Monoclonal gammopathy of undetermined significance (MGUS) and chronic kidney disease (CKD) are common conditions. When monoclonal gammopathy causes CKD it is referred to as monoclonal gammopathy of renal significance (MGRS) and a kidney biopsy is required to confirm the diagnosis. Because of this, some have speculated that MGRS may be severely underdiagnosed and have recommended considering a kidney biopsy in all individuals with MGUS who have microscopic hematuria, proteinuria, or declining estimated glomerular filtration rate (eGFR) of <60 mL/min/1.73m2. If MGRS were more common than previously thought, the prevalence of CKD in persons with MGUS would be expected to be higher than persons without MGUS. We aimed to compare the prevalence of CKD in individuals with and without MGUS in a large, prospective, screened, population-based cohort. Furthermore, we aimed to assess possible association between M protein concentration and kidney function. Methods: A total of 75,422 participants in the Iceland Screens, Treats or Prevents Multiple Myeloma (iStopMM) study were screened for MGUS with serum protein electrophoresis (SPEP), serum free light chains (FLC), and immunofixation (IFE). All previous clinical laboratory samples were obtained, including serum creatinine (SCr), urine albumin/creatinine ratio (ACR) and urinalysis. CKD was defined as SCr-based eGFR of <60 mL/min/1.73m2, or proteinuria or hematuria, present for >90 days. Participants diagnosed with lymphoproliferative disorders or without data on kidney function were excluded. Power analysis demonstrated that this sample size yielded 90% power to detect a 1.5% absolute difference in the prevalence of CKD in persons with and without MGUS. Prevalence of CKD was evaluated using multivariable logistic regression adjusted for age, sex and MGUS status. The association between eGFR and M protein concentration was assessed with linear regression for continuous eGFR and ordinal logistic regression for CKD categories. All models included age and M protein concentration as four knot restricted cubic splines. Sensitivity analyses were performed where CKD was defined solely by persistently lowered eGFR and as a combination of persistently lowered eGFR, proteinuria, and hematuria. Results: A total of 69,120 participants had SCr measurements and 34,294 had urine studies available. MGUS was present in 4,547 (6.6%) participants, of which 2,242 (49.3%) were non-IgM; 703 (15.5%) were IgM; 1,295 (28.5%) were light chain (LC-MGUS); and 307 (6.7%) were biclonal MGUS. A total of 6,680 (9.7%) participants had CKD defined either as eGFR <60 mL/min/1.73 m2 (N=5,915) or persistent proteinuria or hematuria (N=693), or were receiving treatment for end-stage kidney disease (N=74). Participants with MGUS were significantly older (median [IQR] age 69 [60-76] vs 60 [52-69] years) and more predominantly male (55% vs 41%) compared with participants without MGUS. After adjusting for age and sex, no significant association was found between heavy chain MGUS and CKD (odds ratio [OR] 1.00, 95% confidence interval [CI] 0.95-1.17). This also remained true for subgroups of non-IgM MGUS, IgM MGUS, and biclonal MGUS (Table). Participants with LC-MGUS were less likely to have CKD than participants without MGUS (OR 0.39, 95% CI 0.31-0.49, p <0.001). Sensitivity analyses of CKD definition yielded similar results. M protein concentration had a small negative correlation with eGFR (r= -0.08, p<0.001) but when stratified by age and sex category no significant correlation remained. No significant association was found between M protein concentration and worse eGFR category on ordinal logistic regression model adjusted for nonlinear age and sex (OR 1.01, 95% CI, 0.28-3.66). No significant correlation was found between M protein concentration and severity of proteinuria assessed with urine ACR. Conclusion: In this nationwide prospective population-based screening study of nearly 70,000 individuals, we found no association between MGUS and CKD, regardless of whether CKD was defined based on eGFR, urinary findings, or both. Furthermore, we found no association between M protein concentration and eGFR or severity of albuminuria. We conclude that in the absence of multiple myeloma, the results of SPEP, IFE, and serum FLC measurements are of little value in the evaluation of CKD. Furthermore, our results are not consistent with substantial underdiagnosis of MGRS. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Case Report: A case of IgD lambda/lambda Multiple Myeloma in patient with acute renal failure and without monoclonal spike in serum electrophoresis

BackgroundIgD Multiple Myeloma is a rare form of plasma cell dyscrasia and accounts for approximately 1-2% of all cases of Multiple Myeloma. It mainly affects young, male subjects; it is characterized by an aggressive course, a high production of Bence Jones protein, acute renal failure and an often unfortunate outcome compared to the other isotypes of MM. A distinctive feature is the lack of a monoclonal peak on serum protein electrophoresis (SPE).Case reporta 57-year-old man with pain in his left lower limb and weight loss goes to the Emergency Department (Emergency Department). Laboratory tests performed showed normocytic normochromic anemia (Hemoglobin 9.4 g/dL), acute renal failure (s-creatinine 2.85 mg/dL, e-GFR 23 mL/min/1.73 m². serum protein electrophoresis (SPE) detected only mild polyclonal in the gamma zone with no evidence of any monoclonal peak.Resultsserum immunofixation (s-IFE) showed a monoclonal IgD λ band and a monoclonal λ band. The Free Light Chains (s-FLC) measurement showed a ratio of 0.04. The bone marrow biopsy confirmed an infiltration of&amp;gt; 20% of clonal plasma cells; renal biopsy diagnosed “cast nephropathy”.ConclusionIgD λ/λ Multiple Myeloma is a rare form of this disease with a poor prognosis; an early and correct laboratory diagnosis is crucial for appropriate treatment and effective monitoring in order to improve patient outcome.

Serum Free Light Chain Quantification Testing: Comparison of Two Methods for Disease Monitoring.

Levels of free immunoglobulin light chains in serum and urine are a sensitive measure of dysregulated immunoglobulin synthesis. The development of an assay for free light chains in serum was a major advance in laboratory testing for monoclonal gammopathies. The original assay by The Binding Site, called Freelite®, has been in common use in laboratory monitoring of monoclonal gammopathies. Two clinical entities, myeloma-defining condition and light chain-predominant multiple myeloma, rely on quantitative measurements of serum free light chains. Using polyclonal antisera specific to free light chains, Diazyme Laboratories developed a latex immunoturbidimetric assay for quantification of human kappa and lambda serum free light chains. We evaluated the Diazyme assay by comparing the results of kappa and lambda free light chain quantification, and kappa/lambda ratio with the results on the same specimens by the Freelite method. We also compared the correlation of the 2 methods to evaluate response to treatment and to changes in clinical status of patients with multiple myeloma. The results of Freelite and Diazyme methods are comparable. There was no statistically significant difference in the performance of the 2 assays for quantification of light chains, kappa/lambda ratio, or correlation of clinical parameters from patients with multiple myeloma at various stages of monitoring the disease in 2 geographically diverse laboratory and clinical environments. The Diazyme method is comparable to Freelite and provides an opportunity to add the test to front-end automation and improvement in efficiency of the assay.