Abnormal Serum Free Light Chain Ratio Research Articles

Development and validation of a diagnostic nomogram model for predicting monoclonal gammopathy of renal significance

In patients with kidney disease, the presence of monoclonal gammopathy necessitates the exploration of potential causal relationships. Therefore, in this study, we aimed to address this concern by developing a nomogram model for the early diagnosis of monoclonal gammopathy of renal significance (MGRS). Univariate and multivariate logistic regression analyses were employed to identify risk factors for MGRS. Verification and evaluation of the nomogram model's differentiation, calibration, and clinical value were conducted using the receiver operating characteristic (ROC) curve, calibration curve, and decision curve analysis. The study encompassed 347 patients who underwent kidney biopsy, among whom 116 patients (33.4%) were diagnosed with MGRS and 231 (66.6%) with monoclonal gammopathy of undetermined significance. Monoclonal Ig-related amyloidosis (n = 86) and membranous nephropathy (n = 86) was the most common renal pathological type in each group. Notably, older age, abnormal serum-free light chain ratio, and the absence of microscopic hematuria were identified as independent prognostic factors for MGRS. The areas under the ROC curves for the training and verification sets were 0.848 and 0.880, respectively. In conclusion, the nomogram model demonstrated high accuracy and clinical applicability for diagnosing MGRS, potentially serving as a valuable tool for noninvasive early MGRS diagnosis.

Serum-free light chain test utilisation at a South African academic laboratory and comparison with serum protein electrophoresis results.

Serum protein electrophoresis (SPE), urine protein electrophoresis and immunofixation electrophoresis were traditionally utilised for the diagnosis of monoclonal gammopathies. The quantitative serum-free light chain (SFLC) assay is reportedly more sensitive and has been introduced to recent clinical guidelines. This study aimed to investigate SFLC test utilisation and describe SPE findings in patients with abnormal SFLC ratios. A retrospective audit of SFLC analyses was conducted in Cape Town, South Africa, from May 2018 to April 2020. Agreement between abnormal SFLC ratios and SPE results was determined in a sub-group of patients screened for monoclonal gammopathies. Serum-free light chains were analysed using Freelite® Kappa and Lambda assays. Of the 1425 patients included in the audit, 741 (52%) had abnormal SFLC ratios; 636 (45%) had increased and 105 (7%) had decreased SFLC ratios. In a sub-group analysis of 117 new patients with an abnormal SFLC ratio, 57 had a monoclonal protein (M-protein) on SPE (49%), and 60 (51%) did not. Four out of 60 patients without M-protein had a plasma cell dyscrasia, while renal impairment or inflammatory response accounted for the rest. Of the 57 patients with a M-protein and abnormal SFLC ratio, 41 (72%) had a plasma cell dyscrasia, seven (12%) had lymphomas and nine patients (16%) were unclassifiable. Serum-free light chains should be requested when there is a high index of clinical suspicion. Neither SFLC nor SPE should be performed in isolation when screening patients for monoclonal gammopathy, to ensure that no patient is missed. The study adds to the evidence on SFLC test utilisation. Serum protein electrophoresis alone may miss cases of light chain myeloma, while SFLC performed in isolation may produce false positive results in the setting of inflammatory disorders or renal impairment, leading to unnecessary further investigation.

Understanding the Constraints and Optimization of Serum Immunofixation Electrophoresis and Serum Free Light Chains for Detecting Monoclonal Proteins: A Single-Center Experience.

Introduction Serum immunofixation electrophoresis (SIFE) and serum free light chain (SFLC) assay are imperative investigations in diagnosis and follow-up of multiple myeloma (MM). SFLC assays are reported to have higher sensitivity than SIFE. However, discrepancies have been reported between them. The current study was aimed at assessing concordance and discordance between SIFE and SFLC results in MM. Methods A total of 450 observations of both SIFE and SFLC were obtained from treatment-naive and follow-up MM patients. Results One hundred and twenty-nine (28.7%) values were observed as discordant, that is, positive SIFE with normal SFLC ratio or negative SIFE with abnormal SFLC ratio ( p -value < 0.00001). Proportion of discordance was higher in SIFE positive-SFLC normal cases than SIFE negative-SFLC abnormal cases. Discordance was more frequent in follow-up cases. Conclusion Negative SFLC alone may not be reliable for MM follow-up. Algorithm may be based on SFLC measurements on each follow-up till attainment of normal SFLC ratio. Once SFLC normalizes, follow-up may be done with SIFE. If SIFE is positive, further follow-up with SIFE may be initiated.

Clinical characteristics and progression risk factors for patients with monoclonal gammopathy of undetermined significance

Objective: To analyze the clinical presentation and progression risk factors of patients with monoclonal gammopathy of undetermined significance (MGUS) in China. Methods: We retrospectively assessed the clinical features and disease progression of 1 037 patients with monoclonal gammopathy of undetermined significance between January 2004 and January 2022 at Peking Union Medical College Hospital. Results: A total of 1 037 patients were recruited in the study, including 636 males (63.6%) , with a median age of 58 (18-94) years. The median concentration of serum monoclonal protein was 2.7 (0-29.4) g/L. The monoclonal immunoglobulin type was IgG in 380 patients (59.7%) , IgA in 143 patients (22.5%) , IgM in 103 patients (16.2%) , IgD in 4 patients (0.6%) , and light chain in 6 patients (0.9%) . 171 patients (31.9%) had an abnormal serum-free light chain ratio (sFLCr) . According to the Mayo Clinic model for risk of progression, the proportion of patients in the low-risk, medium-low-risk, medium-high risk, and high-risk groups were 254 (59.5%) , 126 (29.5%) , 43 (10.1%) , and 4 (0.9%) , respectively. With a median follow-up of 47 (1-204) months, 34 of 795 patients (4.3%) had disease progression, and 22 (2.8%) died. The overall progression rate was 1.06 (0.99-1.13) /100 person-years. Patients with non-IgM MGUS have a markedly higher disease progression rate per 100 person-years than IgM-MGUS (2.87/100 person-years vs 0.99/100 person-years, P=0.002) . The disease progression rate per 100 person-years in non-IgM-MGUS patients of Mayo classification low-risk, medium-low risk and medium-high risk groups were 0.32 (0.25-0.39) /100 person-years, 1.82 (1.55-2.09) /100 person-years, and2.71 (1.93-3.49) /100 person-years, which had statistically difference (P=0.005) . Conclusion: In comparison to non-IgM-MGUS, IgM-MGUS has a greater risk of disease progression. The Mayo Clinic progression risk model applies to non-IgM-MGUS patients in China.

Body Mass Index and Clinical Factors Associated with Monoclonal Gammopathy of Undetermined Significance (MGUS) Progression in Olmsted County, Minnesota

Introduction Monoclonal gammopathy of undetermined significance (MGUS) is a premalignant clonal disorder, which progresses at a rate of 1% per year to multiple myeloma (MM), or other plasma-cell or lymphoid disorders. MGUS is common and occurs in approximately 3% and 5% of persons 50 and 70 years of age or older, respectively. Clinical factors reported to be associated with MGUS progression include MGUS isotype, abnormal serum free light-chain ratio (FLCr), and high serum monoclonal protein (M protein) level (&amp;gt;=1.5 g per deciliter). Body mass index (BMI) has also been seen associated with MGUS progression, but has not been evaluated in context of established clinical prognostic factors. Here, we evaluate the contribution of BMI to MGUS progression beyond clinical prognostic factors in a population-based study and examine differential associations by sex. Methods We studied 594 patients residing in Olmsted County Minnesota, who were identified with MGUS in a screening study conducted between1995 through 2003. Patients with light-chain MGUS were not included. Patients were screened for M-protein [normal (&amp;lt;1.5 g/dl) or high (≥1.5 g/dl)], FLCr [normal (0.26-1.65) or abnormal (&amp;lt;0.26 and/or &amp;gt;1.65)], and isotype (IgG, IgM, IgA, bi-clonal). Follow-up time was calculated from date of MGUS screening to date of last follow-up, death, or progression to MM or another plasma-cell or lymphoid disorder. BMI (kg/m2) was calculated using height and weight values reported close to sample date (80% of patients within 2 years), and then categorized into BMI&amp;lt;25 and BMI≥25. We used Cox regression to estimate the association of BMI with risk of MGUS progression to MM or another plasma-cell or lymphoid disorder, univariately, and accounting for clinical factors. Analyses were also stratified by sex. We report hazard ratios (HR) and 95% confidence intervals (CI). Results Of the 594 patients, 51% were male, and the median age at screening date was 73 (range:50-98 years). The immunoglobulin type was IgG in 71% of patients, IgM in 17%, IgA in 10%, and bi-clonal in 2%. High M protein level was observed in 22% and abnormal FLCr in 28%. BMI≥25 was observed in 67% of patients. The median follow-up time was 10.5 years (range:0-25). Over a median of 6,846 person-years, 465 patients (78%) died and 57 patients progressed and developed MM (N=39), amyloidosis (N=8), lymphoma (N=5), or Waldenstrom macroglobulinemia (N=5). The overall rate of progression was 0.87 events (CI:0.67-1.12) per 100 person-years, and higher among males (1.01, CI:0.73-1.42) than in females (0.72, CI:0.48-1.08), however, the difference was not statistically significant (P=0.24). In univariate analyses, BMI≥25 (HR=2.14, CI:1.05-4.36, P=0.04), non-IgG isotype (HR=2.84, CI:1.68-4.80, P=0.0001), high M protein (HR=2.57, CI: 1.50-4.42, P=0.001), and abnormal FLCr (HR=3.39, CI:1.98-5.82, P&amp;lt;0.0001) were associated with increased risk of progression (Table 1.A). These four factors were independently associated with MGUS progression in a multivariable model, with a c-statistic=0.75 (CI:0.68-0.82). When stratifying by sex, associations of BMI with progression were stronger among females than males (Table 1.B) [c-statistic=0.81 (CI:0.72-0.90) vs 0.71 (CI:0.60-0.82) for females vs. males respectively], however, a test for interaction between BMI and sex was not statistically significant (P=0.15). Conclusions In this study we found evidence that high BMI is a prognostic factor independent of isotype, M protein, and FLC ratio in the full cohort, however, this was mainly driven by the effect in females rather than males. Future studies should further investigate sex differences in evaluating prognostic factors among MGUS patients. Disclosures Dispenzieri: Intellia: Research Funding; Pfizer: Research Funding; Alnylam: Research Funding; Takeda: Research Funding; Celgene: Research Funding; Janssen: Research Funding. Kumar:Genentech/Roche: Other: Research funding for clinical trials to the institution, Consulting/Advisory Board participation with no personal payments; Cellectar: Other; Kite Pharma: Consultancy, Research Funding; Tenebio: Other, Research Funding; BMS: Consultancy, Research Funding; Karyopharm: Consultancy; MedImmune: Research Funding; Sanofi: Research Funding; Celgene/BMS: Other: Research funding for clinical trials to the institution, Consulting/Advisory Board participation with no personal payments; Janssen Oncology: Other: Research funding for clinical trials to the institution, Consulting/Advisory Board participation with no personal payments; Amgen: Consultancy, Other: Research funding for clinical trials to the institution, Consulting/Advisory Board participation with no personal payments, Research Funding; Merck: Consultancy, Research Funding; Adaptive Biotechnologies: Consultancy; Genecentrix: Consultancy; Takeda: Other: Research funding for clinical trials to the institution, Consulting/Advisory Board participation with no personal payments; Dr. Reddy's Laboratories: Honoraria; AbbVie: Other: Research funding for clinical trials to the institution, Consulting/Advisory Board participation with no personal payments; Novartis: Research Funding; Carsgen: Other, Research Funding; Oncopeptides: Consultancy, Other: Independent Review Committee; IRC member.

Long-Term Follow-up of Monoclonal Gammopathy of Undetermined Significance

BackgroundMonoclonal gammopathy of undetermined significance (MGUS) occurs in approximately 3% of persons 50 years of age or older.MethodsWe studied 1384 patients who were residing in southeastern Minnesota and in whom MGUS was diagnosed at the Mayo Clinic in the period from 1960 through 1994; the median follow-up was 34.1 years (range, 0.0 to 43.6). The primary end point was progression to multiple myeloma or another plasma-cell or lymphoid disorder.ResultsDuring 14,130 person-years of follow-up, MGUS progressed in 147 patients (11%), a rate that was 6.5 times (95% confidence interval [CI], 5.5 to 7.7) as high as the rate in the control population. The risk of progression without accounting for death due to competing causes was 10% at 10 years, 18% at 20 years, 28% at 30 years, 36% at 35 years, and 36% at 40 years. Among patients with IgM MGUS, the presence of two adverse risk factors — namely, an abnormal serum free light-chain ratio (ratio of kappa to lambda free light chains) and a high serum monoclonal protein (M protein) level (≥1.5 g per deciliter) — was associated with a risk of progression at 20 years of 55%, as compared with 41% among patients who had one adverse risk factor and 19% among patients who had neither risk factor. Among patients with non-IgM MGUS, the risk of progression at 20 years was 30% among those who had the two risk factors, 20% among those who had one risk factor, and 7% among those who had neither risk factor. Patients with MGUS had shorter survival than was expected in the control population of Minnesota residents of matched age and sex (median, 8.1 vs. 12.4 years; P<0.001).ConclusionsSignificant differences were noted in the risk of progression between patients with IgM MGUS and those with non-IgM MGUS. Overall survival was shorter among patients with MGUS than was expected in a matched control population. (Funded by the National Cancer Institute.)

Association between abnormal serum free light chains ratio and known prognostic factors in lymphoma; a nephrology viewpoint.

Introduction: The serum immunoglobulin free light chain (FLC) assay quantities of free kappa (κ) and lambda (λ) light chains. This assay has prognostic value in plasma cell proliferative disorders. There are limited data on serum FLC in B-cell malignancies. Objectives: The aim of this study was to compare the known prognostic factors in non-Hodgkin’s lymphoma of the type B-cell and Hodgkin disease with an abnormal secretion amount of light chains in these lymphomas. Patients and Methods: The association of pretreatment FLC and FLC ratio (κ:λ) with previously known prognostic factors for lymphoma such as the international prognostic index (IPI) and B symptoms were evaluated in 50 patients with Hodgkin’s and non-Hodgkin’s lymphoma. IPI is a prognostic score given based on the clinical variables including age, disease stage, serum LDH and extra-nodal involvement. Elevated FLC and an abnormal κ:λ ratio was defined based on the previous publications. Results: The prevalence of abnormal FLC ratio was 38% in all patients and 40.9% in patients with diffuse large B-cell lymphoma. Abnormal FLC ratio was significantly associated with IPI (P=0.04) and B symptoms (P=0.02) in both groups of the patients with Hodgkin’s and non-Hodgkin’s lymphoma. The stage of the disease in Hodgkin’s lymphoma patients showed a significant relationship with the abnormal FLC ratio (P=0.04). Presence of the B symptoms in patients with Hodgkin’s lymphoma had a modest but not statistically significant association with the abnormal FLC ratio (P=0.07). Conclusion: Abnormal FLC ratio as a new potent prognostic biomarker has a significant association with IPI which is the most common clinical tool used to predict outcome in lymphoma patients. Since there is a need for developing a reliable and quantitative prognostic biomarker for lymphoma, evaluation of the independent effect of the abnormal serum FLC ratio is suggested to be considered in future prospective studies. The result of these studies will also be useful for nephrologists, while serum immunoglobulin FLC is capable to damage kidney.

Clinicopathological significance of monoclonal IgA deposition in patients with IgA nephropathy.

Clinicopathological significance of monoclonal IgA deposition and its relation to bone marrow abnormalities in IgA nephropathy (IgAN) remains unclear. We retrospectively investigated the prevalence and clinicopathological significance of monoclonal IgA deposition in 65 patients with IgAN. Serum-free light chain ratio, and urinary Bence Jones protein were also measured. Thirty-nine percent of patients were men, median age was 40 and median observation period was 31months. Five patients (Group M) showed monoclonal IgA lambda deposition and one showed monoclonal IgA kappa deposition. Fifty-nine patients (Group P) showed polyclonal IgA deposition. There were no significant differences in the degree of proteinuria, hematuria and renal function between Group M and Group P. Total protein and albumin were significantly lower in Group M than in Group P. According to the Oxford classification, the percentage of patients with M1 was significantly higher in Group M than in Group P. One patient in Group P showed serum monoclonal IgG lambda. No patient showed abnormal serum-free light chain ratio. Seventy-five percent in Group M and 42% in Group P were treated with steroid. Three patients in Group P progressed to end-stage renal disease (ESRD). The frequency of disappearance of proteinuria or hematuria and progression to ESRD was not different between the groups. The prevalence of monoclonal IgA deposition was 9.2%. Although some parameters differed between the groups, renal outcome were similar. Thus, IgAN with monoclonal IgA deposition seems not to be different entity from those with polyclonal IgA deposition.

The Serum Free Light Chain Assay Allows Earlier Detection of Relapse/Progression of Multiple Myeloma After Autologous Hematopoietic Cell Transplantation

Abstract 4466 The International Myeloma Working Group (IMWG) guidelines use serum free light chain (SFLC) response criteria only in multiple myeloma (MM) patients without measurable M-protein in serum or urine and to satisfy stringent complete remission (sCR) criteria. Current response criteria use changes in intact immunoglobulin measured by serum protein electrophoresis and immunofixation (SIF). The role of the SFLC assay during follow up of MM patients with measurable intact immunoglobulin after autologous hematopoietic cell transplantation (auto-HCT) is not well defined. In order to assess the role of the SFLC assay (Freelite; The Binding Site Group Ltd, Birmingham, UK) during the follow up of MM patients (with measurable M protein in serum or urine), and its role in detecting relapse compared to SIF test, a retrospective analysis of 20 MM patients after melphalan 200 mg/m2 conditioned first auto-HCT was conducted. Patients were followed for a median 15 months (range 3–36 months) between 2008 and 2011. Each patient had both the SFLC assay and SIF performed every 3 months at each routine clinic visit. No patient had renal failure (defined as serum creatinine 2 mg/dl or more). No patient deaths occurred during the follow up period. Two groups were identified. 10 patients without relapse had the following characteristics: median age at HCT 55 years (range 46–68 years); median time from diagnosis to auto-HCT 6.5 months (3–18 months); Durie-Salmon stage IIIA (n=7), stage IA (n=3); IgG kappa (n=5), IgG lambda (n=5); response to HCT very good partial remission VGPR 1 (n=5), CR1 (n=3), and sCR1 (n=2). All patients without relapse maintained a normal SFLC ratio (0.26–1.65) after HCT with negative SIF (n=5), or stable SIF (n=3) and in 2 patients (who were on lenalidomide maintenance), the SIF became negative 12 months and 18 months after HCT. 10 MM patients relapsed after auto-HCT: median age at HCT 55 years (range 46–68 yrs); Durie-Salmon stage IIIA (n=9), IA (n=1); IgG kappa (n=4), IgG lambda (n=2), kappa (n=2), lambda (n=1), IgA kappa (n=1); median time from diagnosis to HCT 8 months (range 4–28 months); response to HCT VGPR1 (n=7), CR1 (n=3). In all the patients who relapsed, the SFLC ratio became abnormal (&lt;0.26 or &gt;1.65) at a median of 3 months (range 3–12 months) before any other test detected relapse, (including SIF, bone marrow biopsy) and the SFLC ratio remained abnormal and continued to worsen over the follow up period. Salvage chemotherapy was begun at a median of 3 months (range 3–12 months) after the SFLC ratio became abnormal after confirmation of relapse by current approved methods (elevation of SIF or bone marrow biopsy). In follow up after HCT, 5 patients who relapsed developed an abnormal SFLC ratio (&lt;0.26 or &gt;1.65) without a concomitant increase in SIF and these patients had bone marrow biopsy confirmation of relapse (25% increase of plasma cells from baseline). In one patient, the SFLC ratio became abnormal at 3 months post HCT with negative SIF, and negative bone marrow biopsy at 3 months after HCT and multiple extramedullary plasmacytomas were found at 4 months after HCT accounting for the relapse. Conclusion: Abnormal SFLC ratio allowed earlier detection of relapse/progression of MM after auto-HCT even in those with measurable M protein in serum and urine and not only in light chain MM but also in those with intact heavy chain immunoglobulins compared to SIF and this can be critical for earlier intervention with salvage strategies. There are currently no guidelines for use of the SFLC assay in follow up of MM patients with measurable serum and urine M protein. The serum free light chain assay should be used concomitantly with serum protein electrophoresis and immunofixation in the follow up of MM patients after auto-HCT. Disclosures: No relevant conflicts of interest to declare.

The Relationship Between Serum Free Light Chain Levels and Urine Protein in Patients with IgG or IgA Myeloma.

Abstract 1810Poster Board I-836The serum free light chain (SFLC) assay is often though to be a replacement for the cumbersome process of 24-hour urine collection for monoclonal protein estimation (http://www.freelite.co.uk/initialinvestigationpro-24.asp; accessed 16 July 2009) despite evidence suggesting that SFLC estimation cannot replace urine protein quantification (Singhal et al. Blood 2007; 109:3611-2). We studied results from patients with IgG or IgA myeloma if all the following criteria were satisfied: concomitant SFLC and 24-hour urine specimens analyzed, no oligoclonal proteins, no diminished free light chain levels (involved or uninvolved). The aim was to study the correlation between SFLC and 24-hour urine total protein (24UTP), 24-hour urine monoclonal protein (24UMP) and urine immunofixation electrophoresis (UIFE). Only concordant abnormal SFLC ratios were considered abnormal (Singhal et al. Blood 2009; 114:38-9). 558 samples in 114 patients were identified. SFLC ratio was abnormal in 242 and normal in 316 (including 2 discordant abnormal). UIFE (available in 540) was negative in 290. The proportion of samples with normal SFLC ratio decreased as 24UTP increased (P<0.001): ≤200 mg - 75% of 243, 200-500 mg 33% of 129, 501-1000 mg - 24% of 54, and >1000 mg - 6% of 32. Similarly, the proportion of samples with normal SFLC ratio declined as 24UMP increased (P=0.001): ≤200 mg (including negative) - 41% of 145, 200-500 mg 4% of 28, 501-1000 mg - 0% of 14, and >1000 mg - 0% of 15. SFLC ratio was normal in 84% of samples with negative UIFE and in 26% of samples with positive UIFE (P<0.0001). Among the 47 samples with abnormal SFLC ratio and negative UIFE, the 24UTP was 47-288 mg (median 112). 24UMP was 35 mg in 1, “faint” in 1, and no restricted bands were seen in ther remaining 45. The table shows the relationship between UPEP, UIFE and SFLC amongst the 540 samples where all 3 tests were available. The presence of any restricted band on UPEP, even if too small to quantify, was considered positive.n=540Positive UPEPNegative UPEPPositive UIFENegative UIFEPositive UIFE22228Negative UIFE17273Abnormal SFLC ratio1725918447Normal SFLC ratio6724266243If a positive UPEP is considered the “gold standard” evidence of the presence monoclonal light chains in the urine, the sensitivity of UIFE in detecting urine monoclonal protein is 93% and that of an abnormal SFLC ratio is 72%. On the other hand, if a positive UIFE is considered the “gold standard” evidence of monoclonal light chains in the urine, the sensitivity of an abnormal SFLC ratio in detecting urine monoclonal protein is 74%. These data, obtained from a much large number of homogeneous clinical samples, confirm our previous observations (Singhal et al. Blood 2007; 109:3611-2) that an abnormal SFLC ratio cannot consistently predict the presence of either non-specific or monoclonal proteinuria. Fortunately, the proportion of urine samples with large aounts of non-specific or monoclonal proteinuria that is associated with normal SFLC ratios is small. The sensitivity of the SFLC ratio in detecting urine monoclonal protein is less than that of UIFE. The SFLC assay cannot replace 24-hour urine collection in clinical practice without compromising patient care. Whether a less cumbersome technique such as a spot (random) urine protein-creatinine ratio - used in conjunction with the SFLC assay - can avert the need for 24-hour urine collections in myeloma patients remains to be investigated. DisclosuresNo relevant conflicts of interest to declare.

Borderline High Serum Free Light Chain κ/λ Ratios Are Seen Not Only in Dialysis Patients but Also in Non–Dialysis-Dependent Renal Impairment and Inflammatory States

We read with interest the article by Abadie et al1 and would like to add our observations that largely corroborate their findings. Abadie et al1 provide confirmatory data that renal reference intervals are required when interpreting the serum free light chain (FLC) ratio in patients suspected of having plasma cell dyscrasias. Because borderline ratios cause significant diagnostic confusion, we were interested to further characterize the clinical characteristics of patients who had borderline abnormal serum FLC ratios and no evidence of plasma cell dyscrasias or lymphoproliferative disorders. We performed a retrospective audit of FLC assays performed between January 1, 2006, and September 13, 2008, at 3 tertiary referral hospitals and correlated cases with borderline abnormal ratios (arbitrarily defined as 0.13–0.25 and 1.66–3.2, ie, 2 times …

The relationship between the serum free light chain assay and serum immunofixation electrophoresis, and the definition of concordant and discordant free light chain ratios

Abstract“Stringent” complete remission in myeloma has been defined by a normal serum free light chain ratio (SFLCR) in addition to the standard criteria for CR. 2648 serial samples from 122 IgG or IgA myeloma patients were studied to explore the relationship between SFLCR and serum immunofixation electrophoresis (SIFE). SFLCR was normal in 34% of cases with positive SIFE and abnormal in 66%. SFLCR was normal in 69% of cases with negative SIFE and abnormal in 31%. When evaluated with SIFE as the benchmark, the sensitivity of SFLCR was 66% and specificity was 69%. These findings were unchanged when abnormal SFLCR values were classified as concordant (< 0.26 for λ disease and > 1.65 for κ) or discordant (< 0.26 for κ disease and > 1.65 for λ). Additional studies are required to determine the temporal relationship between SFLCR normalization and paraprotein clearance. Until then, the role of SFLCR in defining response remains controversial.

Utility of Serum Free Light Chain Analysis When Screening for Lymphoproliferative Disorders

Serum protein electrophoresis (SPE), urine protein electrophoresis (UPE), and immunofixation (IFE) are routinely used to identify the presence of monoclonal immunoglobulin proteins during the investigation of possible monoclonal gammopathies. The purpose of performing urinary Bence-Jones protein (BJP) analysis is to identify monoclonal light chains in the presence or absence of a serum monoclonal component. These tests may be requested for patients in whom the diagnosis is clinically suspected, or may be initiated as a reflex analysis when the results of other tests suggest that multiple myeloma or plasma cell disorders (PCDs) need to be excluded. The serum free light chain (FLC) assay is a sensitive and quantitative technique for measuring FLC concentrations in serum.1 It has been shown to have greater sensitivity than SPE and IFE and can provide an alternative to BJP analysis.2,3 There are a number of problems associated with detecting monoclonal FLCs in urine. FLCs are filtered through the glomeruli of kidney nephrons, then reabsorbed and metabolised via proximal tubules.4,5 Significant quantities of FLCs do not enter the urine unless the reabsorption capacity of the tubules has been overwhelmed and thus do not necessarily reflect either serum FLC levels or tumour production of monoclonal FLCs. However, the most significant problem with urinalysis in a diagnostic setting is poor compliance with the provision of samples. Hill and colleagues reported ~40%6 while Holding and colleagues7 reported ~17%. Retrospective studies have indicated that the majority of patients with monoclonal gammopathies display abnormal serum FLC ratios/levels at presentation: 100% light chain multiple myeloma,8 82% nonsecretory multiple myeloma,9 96% intact immunoglobulin multiple myeloma,10 and 98% AL amyloidosis.11 In addition, approximately one-third of monoclonal gammopathy of undetermined significance (MGUS) patients display abnormal serum FLC ratios, and these patients have an …

B373 Frequency of Abnormal Serum Free Light-Chain Ratio in a French Cohort of Patients with MGUS

B373 Frequency of Abnormal Serum Free Light-Chain Ratio in a French Cohort of Patients with MGUS

The Relationship Between Serum Free Light Chain Levels and Serum Immunofixation Electrophoresis: Implications for the Definition of “Stringent CR” in Myeloma

The serum free light chain (SFLC) assay enables detection of an abnormal protein in patients with plasma cell dyscrasias who secrete no or small quantities of monoclonal protein in the serum. Thus, the SFLC ratio may be abnormal (normal range; 0.26–1.65) in patients who have no M protein on serum immunofixation electrophoresis (SIFE). However, the relationship between the SFLC ratio and abnormal SIFE in patients who do secrete detectable M protein has not been studied.The new international response criteria for myeloma define an entity called stringent complete remission (CR) based on negative SIFE and normal SFLC ratio (with absent clonal plasmacytosis). “CR” is distinguished from “stringent CR” by lack of requirement of normal SFLC ratio in these new criteria. The old criteria did not use SFLC. The new criteria have not been validated prospectively whereas the old criteria have been used in multiple clinical trials.The obvious implication of using normalization of SFLC ratio to define “stringent CR” is that the SFLC ratio is the most sensitive indicator of residual disease. Thus, one would expect to see abnormal SFLC ratio when SIFE is normal but not vice versa. We explored the relationship between SIFE and SFLC ratio in 122 patients with secretory IgG or IgA myeloma. 2648 samples through the continuum of therapy that fulfilled the following criteria were studied: availability of concomitant SFLC and SIFE, and lack of oligoclonal bands on SIFE and UIFE.SIFE showed the original M protein in 2342 samples (88%). SFLC ratio was normal (0.26–1.65) in 1012 (38%). The abnormal ratio was concordant in 1536 and discordant in 100. SFLC ratios were considered concordant if <0.26 for lambda disease and >1.65 for kappa disease, and discordant if <0.26 for kappa disease and >1.65 for lambda disease. Discordant ratios were grouped with normal because they did not reflect an excess of the abnormal light chain associated with the original M protein. If the 95% CI values for SFLC ratio were used (0.3–1.2), 810 (31%) results were normal. With the 95% CI values, the abnormal ratio was concordant in 1702 and discordant in 136.The SFLC ratio was normal in 34% of cases with positive SIFE and abnormal in 66%. On the contrary, the SFLC ratio was normal in 69% of cases with negative SIFE and abnormal in 31%. As the table below shows, the proportion of cases with positive SIFE and normal SFLC ratio was much higher than those with an abnormal SFLC ratio and negative SIFE.SIFESFLC ratioSFLC ratioNormalAbnormalNormal or discordant abnormalConcordant abnormalPositive802 (30%)1540 (58%)874 (33%)1468 (55%)Negative210 (8%)96 (4%)238 (9%)68 (3%)SIFE is currently considered to be the standard indicator of the presence of an M protein. When evaluated against that, the sensitivity of SFLC is 66% and its specificity is 69%. The sensitivity drops to 63% but specificity improves to 77% if discordant abnormal ratios are considered normal.What if either positive SIFE or a concordant abnormal SFLC ratio were considered to indicate residual disease (2410; 91%) and a negative SIFE as well as a normal or discordant abnormal SFLC ratio were required to rule out residual M protein (238; 9%)? In this case, the sensitivity of SIFE is 97% and that of an abnormal concordant SFLC ratio 62%. The assumptions do not allow calculation of specificity.Our data indicate that a normal SFLC ratio cannot rule out the presence of residual disease as conventionally defined by a positive SIFE, and that a normal SFLC ratio is significantly more likely to be seen in the presence of a positive SIFE than is a negative SIFE in the presence of an abnormal SFLC ratio. Additional prospective work is required before SFLC estimation and ratio can be incorporated into assessment of response in myeloma, and to see if the “stringent CR” entity truly defines a more robust disease response than “non-stringent CR.”

The Utility of Serum Free Light Chain Measurement in Myeloma Patients with Oligoclonal Bands on Serum or Urine Immunofixation

During treatment, patients with myeloma can develop restricted bands in the serum or urine that are different from the original M protein on serum (SIFE) and urine (UIFE) immunofixation electrophoresis. These so-called oligoclonal bands represent transient aberrant recovery of the immune system, and are not associated with any adverse implications. Unless SIFE/UIFE are checked and the bands identified as oligoclonal, a mistaken diagnosis of persistent or recurrent disease may be made. It is not known if the pattern of serum free light chain (SFLC) levels helps differentiate between oligoclonal bands and persistent/recurrent M protein.Data on 219 myeloma patients with serial follow-up were evaluated to identify 3537 encounters which fulfilled the following criteria: available SFLC levels, and 1 or more restricted bands identified on SIFE or UIFE. Patients with non-secretory and biclonal disease were excluded. If a heavy or light chain not part of the original M protein was seen, the presence of an oligoclonal band was diagnosed. If the original M protein was identified intact (e.g. the detection of IgG kappa in a patient with IgG kappa myeloma) or its constituent heavy or light chain were identified in an unbound fashion (e.g. the detection of free IgG or free kappa in a patient with IgG kappa myeloma), the original M protein was felt to be present. Results with oligoclonal bands were further characterized by the additional presence or absence of the original M protein.Only the original M protein was seen in 2661 (75%), 352 (10%) had oligoclonal bands without the original M protein, and an oligoclonal band was seen with the original M protein in 524 (15%). The SFLC ratio was normal (0.26–1.65) in 1306 (37%) and abnormal in 2231 (63%).The relationship of the nature of the restricted bands seen with the SFLC ratio was assessed in two ways in preliminary analysis. In the first, the SFLC ratio was classified as normal or abnormal. In the second, abnormal ratios were classified further as concordant (<0.26 for lambda disease and >1.65 for kappa disease) or discordant (<0.26 for kappa disease and >1.65 for lambda disease). Discordant ratios were grouped with normal because they did not reflect an excess of the abnormal light chain associated with the original M protein. The following table shows the relationship between the nature of the restricted bands and the SFLC ratio:SFLC ratioSFLC ratioRestricted band categoryNormalAbnormalNormal or discordant abnormalConcordant abnormalOriginal M protein only843 (32%)1818(68%)919 (35%)1742 (65%)Oligoclonal band(s) only185 (53%)167(47%)215 (61%)137 (39%)Oligoclonal band(s) with original M protein278 (53%)246 (47%)302 (58%)222 (42%)P<0.0001<0.0001As the table shows, the SFLC ratio was normal significantly more frequently when oligoclonal bands were present. This appeared to be unaffected by the presence of bands resembling the original M protein.As the SFLC ratio can be affected by treatment-induced suppression of the uninvolved free light chain, the data were also analyzed as follows: concordant abnormal SFLC ratio with elevated involved free light chain (1890; 53%) versus the rest (1647; 47%). Finally, based on the hypothesis that elevated uninvolved free light chain levels are less likely to be seen with active disease, readings with elevated uninvolved free light chains were transferred from the former category into the latter. The following table shows the relationship between the nature of the restricted bands and the above categories:SFLC ratioSFLC ratioRestricted band categoryNormal (All others)Abnormal (Concordant abnormal with elevated involved free light chain)Normal (All others)Abnormal (Concordant abnormal with elevated involved free light chain; excluding elevated uninvolved free light chain)Original M protein only1246 (47%)1415 (53%)1299 (49%)1362 (51%)Oligoclonal band(s) only247 (70%)105 (30%)257 (73%)95 (27%)Oligoclonal band(s) with original M protein343 (65%)181 (35%)361 (69%)163 (31%)P<0.0001<0.0001Once again, as the table shows, the SFLC ratio was normal (or equivalent of normal) significantly more often when oligoclonal bands were present.We conclude that the SFLC ratio is significantly more likely to be normal when oligoclonal bands are present in patients with myeloma. However, the differences between patients with and without oligoclonal bands are not definitive enough to predict the nature of the bands seen. SIFE and UIFE remain the only definitive means of identifying the nature of the restricted bands seen in patients with myeloma on therapy.

Usefulness of FICTION Method for the Evaluation of Response after Treatment in Multiple Myeloma

Introduction: According to the new uniform response criteria of International Myeloma Working Group (IMWG), stringent complete response (sCR) is defined as a condition of normal free light chain (FLC) ratio and absence of clonal cells in the bone marrow (BM) by immunohistochemistry or immunofluorescence, in addition to the CR condition. The kappa/lambda ratio is assessed to identify clonal cells in the BM and a minimum of 100 plasma cells is required for analysis of clonal cells. However, the evaluation of kappa/lambda ratio by immunohistochemistry or immunofluorescence may be inaccurate, because it is difficult practically to countthe number of anti-kappa/lambda antibodies-stained cells in the BM section and in case of low percentage of residual plasma cells, flow cytometric evaluation is also difficult. To investigate whether FICTION (Fluorescence Immunophenotyping and interphase Cytogenetics as a Tool for the Investigation Of Neoplasms) technique can be used as a tools for evaluation of clonal cells after treatment in multiple myeloma, we performed FICTION on BM cells in follow-up patients with myeloma and compared the results of FICTION with other parameters.Method: 18 myeloma patients, whose BM examination and serum free light chain were checked at the same time after treatment, were enrolled in Seoul National University Hospital. We performed FICTION for the fluorescence in situ hybridization (FISH) items that were abnormal at initial BM examination of each patient. The selected probes were LSI 1q25/1p36/1p subtelomere probe (Vysis, Downers Grobe, IL, USA) for trisomy 1q25, LSI 13 (RB1) 13q14 probe (Vysis) for RB1 deletion, LSI IGH probe (Vysis) for IGH rearrangement and LSI p16 (9p21)/CEP 9 probe (Vysis) for p16 deletion. The FICTION results were reported by the percentage of plasma cells with abnormal FISH signals among plasma cells stained with anti-kappa and lambda antibodies labeled with fluorescein isothiocyanate (FITC). We compared FICTION results with response parameters, such as % plasma cells in BM aspirates, serum FLC ratio, M-component in serum and/or urine protein electrophoresis (PEP) and FISH results.Results: Among 18 patients in follow-up, 5 (28%) showed <5% plasma cells by light microscope based differential count in BM aspirates and normal FISH results below the cut-off level. However, these patients turned out to have clonal cells in BM by FICTION techniques. Among these 5 patients, 3 patients showed abnormal serum FLC ratio and the other 2 patients showed M-component in serum PEP with normal serum FLC ratio. One patient with plasma cells fewer than 5% in BM aspirates, no cytogenetic abnormality in FISH and no M-component in serum, showed abnormal serum FLC ratio and abnormal FICTION results; 2 (25%) of 8 plasma cells showed RB1 deletion in FICTION. After 2 years, this patient progressed to plasma cell leukemia.Conclusion: Results of FICTTON correlated with FLC ratio and/or M-component in serum, while the percentage of plasma cells in BM aspirates or FISH results did not. The assessment of percentage of plasma cells in bone marrow aspirates might be inaccurate due to poor aspiration technique including dilution and focal infiltration of plasma cells. Also, FISH results based on the percentage of abnormal cells among all bone marrow nucleated cells do not reflect clonal plasma cells. In clonclusion, we suggest that FICTION technique is more sensitive method for identification of residual malignant plasma cells with clonalityalong with the evaluation of response after treatment in multiple myeloma.

Evaluation of Serum Free Light Chains and Outcome in Multiple Myeloma Patients with an Intact Monoclonal Immunoglobulin Treated with Autologous Stem Cell Transplantation.

Introduction: The serum free light chain (FLC) assay is a useful tool in diagnosing and monitoring multiple myeloma (MM) patients (pts) with non-secretory and light chain only disease. In addition, the detection of an abnormal serum FLC ratio is an adverse prognostic factor in pts with monoclonal gammopathy of undetermined significance. However, the relationship of the FLC assay to the outcome of patients with an intact monoclonal immunoglobulin following a single autologous stem cell transplantation (ASCT) has not been studied. Thus, the objective of this single centre, retrospective review study was to evaluate the usefulness of the FLC assay as a predictor for response rate and progression free survival (PFS) in this category of pts.Patients & Methods: We identified in our Princess Margaret Hospital MM database a total of 290 pts who underwent a single ASCT between June 2003 and May 2006. Of these, 65 had an intact monoclonal immunoglobulin (IgG in 47, IgA in 16 and IgD in 2) detected at diagnosis plus FLCs measured at referral. Normal range for FLC measurements is as follows: kappa 3.3–13.1 mg/L, lambda 5.7–26.3 mg/L, and kappa/lambda ratio of 0.26–1.65.Results: The median age at diagnosis was 59 years (range, 34–73); 33 (51%) were male. The median time from diagnosis to ASCT was 9.0 months (range, 5.0–29), with a median follow-up time of 27 months (range, 1.0–58.0). Assessment of best response following ASCT revealed that 20 (31%) pts achieved CR/nCR, 21 (32%) VGPR, 21 (32%) PR, 2 (3%) MR, and 1 (2%) was not evaluable for response. No prognostic factors for response were identified. To date, only 9 pts have died and the median overall survival is not yet reached. The median PFS is 25.4 months, with 36 patients progressing after ASCT. An elevated kappa and lambda light chain was detected in 30 (46%) and 22 (34%) of the 65 pts, respectively. Additionally, 52 (82%) of the 65 pts were found to have an abnormal kappa/lambda ratio. There was no significant difference in the PFS of patients with abnormal vs. normal free kappa light chains or FLC ratio. However, a decreased PFS was associated with elevated levels of serum free lambda light chains (p=0.01), β-2 microglobulin (p=0.007) and LDH (p=0.01).Conclusions:The majority of pts with an intact monoclonal immunoglobulin also have an abnormally high level of the corresponding serum FLC and an abnormal FLC ratio;an elevated serum free lambda level as well as increased β-2 microglobulin and LDH levels, as previously described, were identified as adverse prognostic factors for PFS in this population;we continue to routinely assess serum FLC for all pts at referral; however, longer follow-up is needed to further evaluate the prognostic significance of this parameter on the clinical outcome of pts.

Immunoglobulin free light chains and solitary plasmacytoma of bone

AbstractAn abnormal serum immunoglobulin free light chain (FLC) ratio at diagnosis may identify risk of progression to myeloma in patients with solitary bone plasmacytoma (SBP). In the cohort of 116 patients, 43 have progressed to myeloma, with a median time to progression of 1.8 years. The FLC ratio was determined in all 116 patients on serum collected at time of diagnosis and was abnormal in 54 patients (47%). An abnormal FLC ratio was associated with a higher risk of progression to myeloma (P = .039). The risk of progression at 5 years was 44% in patients with an abnormal serum FLC ratio at diagnosis compared with 26% in those with a normal FLC ratio. One to 2 years following diagnosis, a persistent serum M protein level of 5 g/L (0.5 g/dL) or higher was an additional risk factor for progression. A risk stratification model was constructed using the 2 variables of FLC ratio and M protein level: patients with a normal FLC ratio at baseline and M protein level less than 5 g/L (0.5 g/dL) at 1 to 2 years following diagnosis (low risk, n = 31); with either risk factor abnormal (intermediate risk, n = 26); and with both an abnormal FLC ratio and M protein level of 5 g/L (0.5 g/dL) or higher (high risk, n = 18). The corresponding progression rates at 5 years were significantly different in the low, intermediate, and high groups: 13%, 26%, and 62%, respectively (P < .001).

Serum Free Light Chain Measurement Can Replace Urine Electrophoresis in the Detection of B Cell Proliferative Disorders.

Retrospective studies have established the high sensitivity of quantitative serum free light chain (SFLC) measurement in the detection of patients with light chain myeloma, nonsecretory myeloma and primary amyloidosis. These disorders account for 15–20% of new diagnoses of B cell proliferative disorders and cannot be confidently excluded by current protocols without electrophoresis of both serum and urine. This prospective study evaluated whether the addition of SFLC to our first line investigations for B cell proliferative disorders detected additional patients with monoclonal gammopathies and if SFLC could replace the requirement for urine for Bence Jones Protein (BJP) analysis. SFLC were added to consecutive requests for serum electrophoresis (SPE) received to investigate patients for possible B-cell proliferative disorders over a 4 month period. SFLC was measured by immunoturbidimetry (The Binding Site, Birmingham, UK) in 923 patients. Subjects with known B-cell disorders were excluded. Concurrent urine samples were received from 370 patients for BJP(40%). The Hydrasis system was used for SPE, urine electrophoresis (UEP) and urine and serum immunofixation (Sebia, Issy-Les-Moulineaux, France.) Kappa/Lambda FLC ratio was abnormal in 71 (7.7%) patients. In 28 of these cases the SPE showed a possible monoclonal band or hypoglobulinaemia and subsequent serum immunofixation confirmed a monoclonal band in 19. In the remaining 43 with negative SPE but abnormal SFLC ratios, lymphoma was diagnosed in 1, multiple myeloma in 2 and monoclonal gammopathy of undetermined significance in 3. Follow-up is continuing in 3 further patients. Of 15 patients with positive urine BJP, 4 patients had normal SFLC ratios but did not have lymphoproliferative disorders requiring treatment. Additional diagnostic information was gained by adding SFLC to SPE for first line investigation of possible B cell disorders. 6 additional patients were identified by abnormal SFLC ratios. Replacing BJP with SFLC ratio would not have missed any significant pathology. In the light of this study we have adopted SPE and SFLC as our first line tests for the investigation of possible B cell disorders. The quality of our diagnostic service has improved; urine samples were received from only 40% of patients being screened and SFLC analysis allows the more confident exclusion of light chain disorders in the absence of a urine sample. The availability of SFLC results when viewing SPE gels assists in the interpretive process and highlights samples requiring serum immunofixation to identify monoclonal bands in the alph-2 or beta globulin regions or light chain monoclonal bands too small for reliable detection by SPE.