Urine immunofixation electrophoresis and serum free light chain analyses benefit diagnosis of multiple myeloma in orthopedic patients with normal serum total proteins, creatinine, calcium, and hemoglobin.

BACKGROUND: A substantial number of patients with multiple myeloma (MM) who have bone destruction are initially admitted into the orthopedic service at the hospital. However, routine laboratory testing usually fails to identify these patients, thus delaying optimal therapy. Therefore, there is a clear medical need for early diagnosis of MM in these patients. METHODS: Between 2019 and 2021, 42 patients receiving treatment for orthopedic conditions had normal hemoglobin (Hb), total protein (TP), albumin (ALB), creatinine (CREA), and blood calcium (Ca) levels before their surgical procedure(s) but were subsequently pathologically confirmed to have MM, based on their presenting orthopedic symptoms. During the same period, 52 patients with orthopedic conditions were pathologically excluded from the diagnosis of MM and were recruited into our control group. Serum free light chain (sFLC) testing was performed in 94 consecutive patients in the orthopedic service using Siemens N Latex FLC kits. The levels of Hb, TP, ALB, CREA, and Ca were also measured. All 42 patients with MM were divided into group A (n = 25: κ proliferation) and group B (n = 17: λ proliferation) by the pathology department. RESULTS: There were no significant differences in levels of Hb, TP, ALB, CREA, and Ca between group A and group B and the control group. However, the sFLC κ/λ ratio of group A and B was also significantly different from that of the control group (P < .001). The results of serum immunofixation electrophoresis (IFE) testing demonstrated negative results in 14 cases (58.3%) in group A and 4 cases (25.0%) in group B. CONCLUSIONS: Some patients with orthopedic conditions who do not have typical MM laboratory results, such as those with abnormal Hb, TP, ALB, CREA, and Ca levels before their operation(s), actually have MM. MM should be highly suspected in patients with unexplained bone lesions and with an abnormal sFLC κ/λ ratio. Further tissue or bone marrow biopsy is needed in these patients even if serum and urine IFE results are negative and light chain ratio is normal.

Quantification of Free Immunoglobulin Light Chains in Urine.

BACKGROUND: The serum-free immunoglobulin light chain assay has been recommended as a screening test for monoclonal gammopathy. We evaluated the usefulness of urine free immunoglobulin light concentration for selection of specimens for immunofixation electrophoresis. METHODS: Using kits from The Binding Site for Freelite ®, we validated examination of urine for measuring free κ and λ light chains. The results of urine free light chain concentrations were evaluated to ascertain if the results could be used to reduce the number of specimens requiring urine protein immunofixation electrophoresis. RESULTS: In the 515 specimens examined, there was no evidence of monoclonal gammopathy or history of monoclonal gammopathy in 331. Monoclonal κ or λ light chains were detectable in 42 and 30 specimens, respectively. There was history of κ or λ chain associated monoclonal gammopathy in 62 and 50 patients, respectively. In the 38 monoclonal κ positive urine specimens, with light chain data, κ/λ ratio was >5.83 in all specimens. In 27 specimens positive for monoclonal λ light chains, with light chain data, the urine λ/κ ratio was > 0.17 in 24 of 27 specimens and > 0.041 in all specimens. In patients without monoclonal gammopathy all specimens had a κ/λ ratio of >5.83 or λ/κ ratio >0.17. CONCLUSIONS: The Freelite ® assay from The Binding Site is suitable for quantification of free light chains in urine. In patients with known history of monoclonal gammopathy, urine immunofixation electrophoresis may be omitted in specimens with κ/λ ratio of <5.83 for κ associated lesions and λ/κ ratio of <0.041 for λ associated lesions. However, the results do not support using this test for first-time urine testing for monoclonal light chains as it is not predictive of positive result, nor does it exclude a monoclonal light chain in urine.

Mono/polyclonal free light chains as challenging biomarkers for immunological abnormalities.

Free light chain (FLC) kappa (k) and lambda (λ) consist of low molecular weight proteins produced in excess during immunoglobulin synthesis and secreted into the circulation. In patients with normal renal function, over 99% of FLCs are filtered and reabsorbed. Thus, the presence of FLCs in the serum is directly related to plasma cell activity and the balance between production and renal clearance. FLCs are bioactive molecules that may exist as monoclonal (m) and polyclonal (p) FLCs. These have been detected in several body fluids and may be key indicators of ongoing damage and/or illness. International guidelines now recommend mFLC for screening, diagnosis and monitoring multiple myeloma and other plasma cell dyscrasias. In current clinical practice, FLCs in urine indicate cast nephropathy and other renal injury, whereas their presence in cerebrospinal fluid is important for identifying central nervous system inflammatory diseases such as multiple sclerosis. Increased pFLCs have also been detected in various conditions characterized by B cell activation, i.e., chronic inflammation, autoimmune disease and HCV infection. Monitoring the coronavirus (COVID-19) pandemic by analysis of salivary FLCs presents a significant opportunity in clinical immunology worthy of scientific pursuit.

Immune-Related Urine Biomarkers for the Diagnosis of Lupus Nephritis.

The kidney is one of the main organs affected by the autoimmune disease systemic lupus erythematosus. Lupus nephritis (LN) concerns 30-60% of adult SLE patients and it is significantly associated with an increase in the morbidity and mortality. The definitive diagnosis of LN can only be achieved by histological analysis of renal biopsies, but the invasiveness of this technique is an obstacle for early diagnosis of renal involvement and a proper follow-up of LN patients under treatment. The use of urine for the discovery of non-invasive biomarkers for renal disease in SLE patients is an attractive alternative to repeated renal biopsies, as several studies have described surrogate urinary cells or analytes reflecting the inflammatory state of the kidney, and/or the severity of the disease. Herein, we review the main findings in the field of urine immune-related biomarkers for LN patients, and discuss their prognostic and diagnostic value. This manuscript is focused on the complement system, antibodies and autoantibodies, chemokines, cytokines, and leukocytes, as they are the main effectors of LN pathogenesis.

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.

Indicators of profound hematologic response in AL amyloidosis: complete response remains the goal of therapy.

In AL amyloidosis complete response (aCR) is defined as negative serum and urine immunofixation with normalized free light chain ratio (FLCR). However, achievement of low levels of involved FLC (iFLC) or difference between iFLC and uninvolved FLC (dFLC) are also relevant endpoints for treatment. We divided 434 consecutive patients with AL amyloidosis into five groups according to response 6 months after treatment initiation: aCR, iFLC <20 mg/L, normalized-iFLC, dFLC <10 mg/L, and normalized FLC ratio. Overall survival (OS) was similar (median not reached) in patients in aCR and in those who reached iFLC <20 mg/L, while it was inferior in all other groups (medians ranging from 79 to 91 months). Time to next therapy or death (TNTD) was longer in subjects attaining aCR (median 69 months) than in subjects reaching any FLC endpoint (medians ranging from 18 to 39 months). The ability of discriminating patients who survived more than 2 years among all responders was greater for current definition of aCR compared to combination of negative serum and urine immunofixation with any low-FLC endpoint. Complete response predicts best outcomes in AL amyloidosis and should be the goal of therapy if tolerability allows.

Refining amyloid complete hematological response: Quantitative serum free light chains superior to ratio.

Response assessment in light chain (AL) amyloidosis is based on serum and urine monoclonal protein studies. Newly diagnosed patients (n = 373) who achieved very good partial response or complete response (CR) to first line therapy were assessed for the survival impact of each of the monoclonal protein studies. At end of therapy (EOT), negative serum/urine immunofixation (IFE) was achieved in 61% of patients, 72% achieved normal serum free light chain ratio (sFLCR), and the median involved free light chain (iFLC) and difference between involved to uninvolved light chain (dFLC) were 17 mg/L and 5 mg/L, respectively. Overall, 46% of patients achieved a CR at EOT. At EOT, iFLC ≤20 mg/L and dFLC ≤10 mg/L were additive in survival discrimination to negative serum/urine IFE and were independent predictors of overall survival. In contrast, normalization of sFLCR did not add survival discrimination to serum/urine IFE and was not independent predictor of survival. We propose a new definition for hematological CR to include serum/urine IFE negativity plus iFLC ≤20 mg/L or dFLC ≤10 mg/L, instead of the current definition of serum/urine IFE negativity and normal sFLCR. Complete response using dFLC ≤10 mg/L had the best performance in those with significant renal dysfunction and by light chain isotype, making it the preferred partner to IFE. Validation of these results in a multicenter cohort is warranted.

Clinical characteristics and outcomes of oligosecretory and non-secretory multiple myeloma.

Secretion of monoclonal immunoglobulins (MIg) detected in the serum and/or urine is one of the typical features of multiple myeloma (MM). However, some patients secrete MIg in quantities below "measurable" (termed oligosecretory MM) and others have no detectable MIgs by standard serum and urine immunofixation (termed non-secretory MM). In a cohort of 852 consecutive patients with active myeloma, we identified 100 (11.7%) patients with oligo/non-secretory MM, including 20 (2.3%) with non-secretory MM. Compared to patients with secretory MM, these were younger, less anemic, and had less often renal dysfunction and less extensive bone marrow infiltration. Presence and extent of bone disease were similar, however, hypercalcemia was less common and more often is ISS (International Staging System)-1 and, in those with available FISH (Fluoresense In Situ Hybridization) , high-risk cytogenetics were less common. FLCs (Free Light Chains) were available in 17 patients with non-secretory MM: only 3 had normal FLC ratio; the others had abnormal ratio and 9/14 had involved FLC ≥ 100 mg/L. The 4-year OS for patients with oligo/non-secretory disease was 64% vs 58% for secretory MM. In multivariate analysis, oligo/non-secretory disease was not an independent prognostic factor per se. Thus, 12% of MM patients present with oligo/non-secretory disease at diagnosis and have different biologic characteristics but similar outcome to other MM patients.

Epidemiological and immunochemical parameters of monoclonal plasma cell dyscrasias of 2121 cases in Algeria.

BACKGROUND: Plasma cell dyscrasias (PCD) are a heterogeneous group of diseases characterized by the expansion of monoclonal bone marrow plasma cells that produce a monoclonal immunoglobulin (M-component). PURPOSE: This is a retrospective study that describes the epidemiological, immunochemical features and etiology of monoclonal gammopathies diagnosed between 1998 and 2016 in the Teaching Hospital Beni-Messous of Algiers. PATIENTS AND METHODS: 2121 cases of monoclonal gammopathies (MG) were collected during this period. Serum/urine protein electrophoresis, serum/urine immunofixation and serum free light chain measurements were used to demonstrate M protein. RESULTS: The middle age of the patients at the time of the diagnosis were 62.96 ± 13.19 years with extremes ranging from 07 to 99 years. The study included 1013 (47, 76 %) men and 1108 (52, 23 %) women with a sex ratio 0,91. Isotypes repartition was: IgG (60.91 %), IgA (17.91 %), light chain (10.46 %), IgM (6.6 %), IgD (1.03 %) and IgE (0.09 %) of cases. The most frequent diagnosis was: Multiple Myeloma (55.20 %), followed by monoclonal gammopathy of undetermined significance (34.13 %). CONCLUSION: In our study, two particularities were noted. There is no male predominance in Algerian PCD patients. Moreover, we observed a higher frequency of light chain multiple myeloma and lower frequency of IgM isotype compared to western studies.

Urine and Free Immunoglobulin Light Chains as Analytes for Serodiagnosis of Hantavirus Infection.

Rapid point-of-care testing is a megatrend in infectious disease diagnosis. We have introduced a homogeneous immunoassay concept, which is based on the simultaneous binding of antigen and protein L to a given immunoglobulin molecule. The complex formation is detected utilizing time-resolved Förster resonance energy transfer between antigen-attached donor and acceptor-labeled protein L, hence the name LFRET. Here, we demonstrate that urine can be used as a sample matrix in LFRET-based serodiagnostics. We studied urine samples collected during the hospitalization and recovery of patients with acute Puumala orthohantavirus (PUUV) infection. We compared PUUV antibody-specific LFRET signals in urine to those in plasma, and found excellent correlation in the test outcomes The LFRET test from urine was positive in 40/40 patients with acute PUUV infection. PUUV causes a mild form of hemorrhagic fever with renal syndrome, characterized by acute kidney injury and proteinuria. Immunofluorescence and western blotting demonstrated PUUV-IgG and -IgA in urine, however, the presence of intact immunoglobulins did not fully explain the LFRET signals. We purified free light chains (FLCs) from both urine and serum of healthy volunteers and patients with acute PUUV infection, and verified the presence of antigen-specific FLCs. Antigen-specific FLCs provide a new means for non-invasive antibody detection and disease diagnosis.

Responses in multiple myeloma should be assigned according to serum, not urine, free light chain measurements.

The most recent update to the International Myeloma Working Group consensus criteria places a strong emphasis on the need for more sensitive haematological markers of response driven by the success of novel therapies. One such marker is serum free light chain (sFLC) analysis, which was first incorporated into the definition of stringent complete response in 2006. However, over the past decade there has been some reluctance to extend the role of the sFLC assays to replace 24 h urine electrophoresis for monitoring multiple myeloma (MM). In this review, we lay out the evidence in favour of serum over urine for monoclonal FLC measurements and propose modified criteria for response assignment in myeloma.

The FLC dimer with lambda type may false-migrate to the position of "albumin" band by urine protein electrophoresis on Sebia agarose gel-based detection system.

BACKGROUND: Monoclonal free light chains (FLC) commonly exist in monomeric or dimeric forms but rarely as larger molecules. Little is known about whether polymeric molecules can affect urine protein electrophoresis (UPE) results. METHODS: Urine samples were collected from 72 multiple myeloma (MM) patients with Bence Jones protein (BJP). Urine protein and immunofixation electrophoresis were analyzed on Sebia SDS "agarose" gel electrophoresis system (SDS-AGE), and immunoglobulin free light chains were measured on the BNII nephelometric assay. RESULTS: A type of disulfide-bound FLC dimer shows a pattern shift to the position of the "albumin" band in urine protein electrophoresis in multiple myeloma (MM) patients according to the Sebia agarose gel-based detection system, which was validated by immunofixation, SDS-PAGE, and mass spectrometric methods. Similar cases were found in 21 (29.17%) of 72 MM patients with BJP, and 19 (90.5%) of 21 patients were the lambda type. CONCLUSIONS: These results indicate that BJP with lambda type has a strong tendency to abnormally migrate, which may increase the risk of misinterpretation of protein electrophoresis in clinics. Thus, when the urine protein electrophoresis is inconsistent with the result by nephelometric method, urine protein electrophoresis needs to be repeated on the deduced condition to confirm the essence of the originally identified "albumin."

Serum free light chain measurements to reduce 24-h urine monitoring in patients with multiple myeloma with measurable urine monoclonal protein.

Detection of myeloma progression (PD) relies on serial 24-h urinary M protein measurements in patients without measurable serum M spike. We examined whether serial difference free light chain (dFLC) levels could be used as a surrogate for serial 24-h urine M protein measurements in monitoring for PD in patients with baseline measurable urine M protein. We studied 122 patients who had serial measurement of urine M protein and serum FLC and had demonstrated PD. The median increase in dFLC with progression as defined by urine M spike was 110% (IQR: 55-312) and median absolute increase was 74 mg/dL; while 89% of patients had dFLC increase ≥ 25%, 94% had absolute increase in dFLC > 10 mg/dL, and 98% met at least 1 of these 2 criteria at PD. In patients with baseline measurable serum FLC (n = 118), 89% had increase in dFLC ≥ 25%, 97% had dFLC increase of > 10 mg/dL, and 98% had 1 of the 2. We conclude that serial dFLC assessments can be used in place of serial 24-h urine protein assessments during myeloma surveillance to monitor for PD. Once patients have an absolute increase in dFLC of >10 mg/dL from the nadir, a 24-h urine collection can then be assessed to document PD as per the International Myeloma Working Group criteria.

Light Chain Cast Nephropathy: Practical Considerations in the Management of Myeloma Kidney-What We Know and What the Future May Hold.

PURPOSE OF REVIEW: To update and evaluate the current knowledge on pathogenesis and management of light chain cast nephropathy. Light chain cast nephropathy (LCCN) is the leading cause of acute renal failure in patients with multiple myeloma and is currently recognized as a myeloma defining event. RECENT FINDINGS: The immunoglobulin free light chain plays an integral role in the pathogenesis of LCCN. The level of free light chain (FLC) in the blood and urine is directly associated with the risk of developing LCCN. Recovery of renal function is related to the speed and degree of the serum FLC reduction. Recently, two randomized trials using high cutoff dialyzer for the removal of serum FLC produced different results in terms of renal recovery. FLC plays a key role in the development and resolution of LCCN. Future therapies will aim to rapidly reduce its concentration or interrupt its interaction with Tamm-Horsfall protein.

Multiple Myeloma and Its Precursor Disease Among Firefighters Exposed to the World Trade Center Disaster.

Importance: The World Trade Center (WTC) attacks on September 11, 2001, created an unprecedented environmental exposure to known and suspected carcinogens suggested to increase the risk of multiple myeloma. Multiple myeloma is consistently preceded by the precursor states of monoclonal gammopathy of undetermined significance (MGUS) and light-chain MGUS, detectable in peripheral blood. Objective: To characterize WTC-exposed firefighters with a diagnosis of multiple myeloma and to conduct a screening study for MGUS and light-chain MGUS. Design, Setting, and Participants: Case series of multiple myeloma in firefighters diagnosed between September 11, 2001, and July 1, 2017, together with a seroprevalence study of MGUS in serum samples collected from Fire Department of the City of New York (FDNY) firefighters between December 2013 and October 2015. Participants included all WTC-exposed FDNY white, male firefighters with a confirmed physician diagnosis of multiple myeloma (n = 16) and WTC-exposed FDNY white male firefighters older than 50 years with available serum samples (n = 781). Exposures: WTC exposure defined as rescue and/or recovery work at the WTC site between September 11, 2001, and July 25, 2002. Main Outcomes and Measures: Multiple myeloma case information, and age-adjusted and age-specific prevalence rates for overall MGUS (ie, MGUS and light-chain MGUS), MGUS, and light-chain MGUS. Results: Sixteen WTC-exposed white male firefighters received a diagnosis of multiple myeloma after September 11, 2001; median age at diagnosis was 57 years (interquartile range, 50-68 years). Serum/urine monoclonal protein isotype/free light-chain data were available for 14 cases; 7 (50%) had light-chain multiple myeloma. In a subset of 7 patients, myeloma cells were assessed for CD20 expression; 5 (71%) were CD20 positive. In the screening study, we assayed peripheral blood from 781 WTC-exposed firefighters. The age-standardized prevalence rate of MGUS and light-chain MGUS combined was 7.63 per 100 persons (95% CI, 5.45-9.81), 1.8-fold higher than rates from the Olmsted County, Minnesota, white male reference population (relative rate, 1.76; 95% CI, 1.34-2.29). The age-standardized prevalence rate of light-chain MGUS was more than 3-fold higher than in the same reference population (relative rate, 3.13; 95% CI, 1.99-4.93). Conclusions and Relevance: Environmental exposure to the WTC disaster site is associated with myeloma precursor disease (MGUS and light-chain MGUS) and may be a risk factor for the development of multiple myeloma at an earlier age, particularly the light-chain subtype.

Concurrent structural and biophysical traits link with immunoglobulin light chains amyloid propensity.

Light chain amyloidosis (AL), the most common systemic amyloidosis, is caused by the overproduction and the aggregation of monoclonal immunoglobulin light chains (LC) in target organs. Due to genetic rearrangement and somatic hypermutation, virtually, each AL patient presents a different amyloidogenic LC. Because of such complexity, the fine molecular determinants of LC aggregation propensity and proteotoxicity are, to date, unclear; significantly, their decoding requires investigating large sets of cases. Aiming to achieve generalizable observations, we systematically characterised a pool of thirteen sequence-diverse full length LCs. Eight amyloidogenic LCs were selected as responsible for severe cardiac symptoms in patients; five non-amyloidogenic LCs were isolated from patients affected by multiple myeloma. Our comprehensive approach (consisting of spectroscopic techniques, limited proteolysis, and X-ray crystallography) shows that low fold stability and high protein dynamics correlate with amyloidogenic LCs, while hydrophobicity, structural rearrangements and nature of the LC dimeric association interface (as observed in seven crystal structures here presented) do not appear to play a significant role in defining amyloid propensity. Based on the structural and biophysical data, our results highlight shared properties driving LC amyloid propensity, and these data will be instrumental for the design of synthetic inhibitors of LC aggregation.