A markedly elevated serum free light chain (FLC) ratio may serve as a biomarker for malignant transformation in high-risk smoldering multiple myeloma (SMM) and identify patients who are at imminent ...risk of progression. We retrospectively studied the predictive value of the serum (FLC) assay in 586 patients with SMM diagnosed between 1970 to 2010. A serum involved/uninvolved FLC ratio ≥ 100 was used to define high-risk SMM, which included 15% (n=90) of the total cohort. Receiver operating characteristics analysis determined the optimal FLC ratio cut-point to predict progression to symptomatic multiple myeloma (MM) within 2 years of diagnosis, which resulted in a specificity of 97% and sensitivity of 16%. Fifty-six percent of patients developed progressive disease during median follow-up of 52 months, but this increased to 98% in the subgroup of patients with FLC ratio ≥ 100. The median time to progression in the FLC ratio ≥ 100 group was 15 months versus 55 months in the FLC <100 group (P<0.0001). The risk of progression to MM within the first 2 years in patients with an FLC ratio ≥ 100 was 72%; the risk of progression to MM or light chain amyloidosis in 2 years was 79%. We conclude that a high FLC ratio ≥ 100 is a predictor of imminent progression in SMM, and such patients may be considered candidates for early treatment intervention.
Multiple myeloma (MM) incidence is markedly higher in blacks compared with whites, which may be related to a higher prevalence of monoclonal gammopathy of undetermined significance (MGUS). Our ...objective was to define the prevalence and risk factors of MGUS in a large cohort representative of the US population. Stored serum samples from the National Health and Nutritional Examination Survey (NHANES) III or NHANES 1999-2004 were available for 12,482 individuals of age ⩾50 years (2331 'blacks', 2475 Hispanics, 7051 'whites' and 625 'others') on which agarose-gel electrophoresis, serum protein immunofixation, serum-free light-chain assay and M-protein typing were performed. MGUS was identified in 365 participants (2.4%). Adjusted prevalence of MGUS was significantly higher (P<0.001) in blacks (3.7%) compared with whites (2.3%) (P=0.001) or Hispanics (1.8%), as were characteristics that posed a greater risk of progression to MM. The adjusted prevalence of MGUS was 3.1% and 2.1% for the North/Midwest versus South/West regions of the United States, respectively (P=0.052). MGUS is significantly more common in blacks, and more often has features associated with higher risk of progression to MM. A strong geographic disparity in the prevalence of MGUS between the North/Midwest versus the South/West regions of the United States was found, which has etiologic implications.
We hypothesized that the suppression of uninvolved immunoglobulin in monoclonal gammopathy of undetermined significance (MGUS) as detected by suppression of the isotype-specific heavy and light chain ...(HLC-pair suppression) increases the risk of progression to malignancy. This approach required quantitation of individual heavy/light chains (for example, IgGλ in IgGκ MGUS patients). Of 1384 MGUS patients from Southeastern Minnesota seen at the Mayo Clinic from 1960 to 1994, baseline serum samples obtained within 30 days of diagnosis were available in 999 persons. We identified HLC-pair suppression in 27% of MGUS patient samples compared with 11% of patients with suppression of uninvolved IgG, IgA or IgM. HLC-pair suppression was a significant risk factor for progression (hazard ratio (HR), 2.3; 95% confidence interval (CI) 1.5-3.7; P<0.001). On multivariate analysis, HLC-pair suppression was an independent risk factor for progression to malignancy in combination with serum M-spike size, heavy chain isotype and free light chain ratio (HR, 1.8; 95% CI, 1.1-3.00; P=0.018). The finding that HLC-pair suppression predicts progression in MGUS and occurs several years before malignant transformation has implications for myeloma biology.
The quantitative assay for free light chains (FLCs) is a recently introduced commercial test reported to be sensitive and specific for detecting FLC diseases such as primary systemic amyloidosis ...(AL), light chain deposition disease (LCDD), nonsecretory multiple myeloma (NSMM), and light chain multiple myeloma. We evaluated its diagnostic performance in clinical practice.
All FLC clinical test results generated in 2003 were abstracted from the Laboratory Information System. Diagnoses were obtained from the Dysproteinemia database and the patient medical history.
In 2003, we received samples for FLC assays from 1020 Mayo Clinic patients. The majority of these patients (88%) had bone marrow-derived monoclonal plasma cell disorders (PCDs). The 121 patients who did not have monoclonal gammopathy all had FLC kappa/lambda ratios within the range of values obtained for a reference population in our laboratory. Among the patients with monoclonal gammopathies were patients with multiple myeloma (330), AL (269), monoclonal gammopathy of undetermined significance (114), smoldering multiple myeloma (72), plasmacytoma (22), NSMM (20), macroglobulinemia (9), LCDD (7), and a variety of other PCDs. Among the 110 AL patients who had not been previously treated and who had a FLC assay performed within 120 days of diagnosis, the FLC kappa/lambda ratio was positive in 91% compared with 69% for serum immunofixation electrophoresis (IFE) and 83% for urine IFE. The combination of serum IFE and serum FLC assay detected an abnormal result in 99% (109 of 110) of patients with AL.
The performance of the FLC assay in this analysis of clinical laboratory data is consistent with results from published retrospective validation studies.
We hypothesized that the presence of monoclonal free kappa or lambda immunoglobulin light chains in monoclonal gammopathy of undetermined significance (MGU225), as detected by the serum free light ...chain (FLC) assay increases the risk of progression to malignancy. Of 1384 patients with MGUS from Southeastern Minnesota seen at the Mayo Clinic from 1960 to 1994, baseline serum samples obtained within 30 days of diagnosis were available in 1148. At a median follow-up of 15 years, malignant progression had occurred in 87 (7.6%) patients. An abnormal FLC ratio (kappa-lambda ratio < 0.26 or > 1.65) was detected in 379 (33%) patients. The risk of progression in patients with an abnormal FLC ratio was significantly higher compared with patients with a normal ratio (hazard ratio, 3.5; 95% confidence interval CI, 2.3-5.5; P < .001) and was independent of the size and type of the serum monoclonal (M) protein. Patients with an abnormal serum FLC ratio, non–immunoglobulin G (non-IgG) MGUS, and a high serum M protein level (≥ 15 g/L) had a risk of progression at 20 years of 58% (high-risk MGUS) versus 37% with any 2 of these risk factors (high-intermediate risk), 21% with one risk factor (low-intermediate risk), and 5% when none of the risk factors were present (low risk).
Serum from almost 80 percent of the residents of Olmsted County, Minnesota, was screened for the presence of a monoclonal gammopathy of undetermined significance. Small amounts of monoclonal ...immunoglobulin were found in 3.2 percent of persons 50 years of age or older and in 5.3 percent of persons 70 years of age or older.
Small amounts of monoclonal immunoglobulin were found in 3.2 percent of persons 50 years of age or older and in 5.3 percent of persons 70 years of age or older.
Although multiple myeloma is the prototypical monoclonal gammopathy, the most common plasma-cell disorder is the premalignant precursor of myeloma, monoclonal gammopathy of undetermined significance (MGUS). MGUS is defined by a monoclonal immunoglobulin concentration in serum of 3 g per deciliter or less; the absence of lytic bone lesions, anemia, hypercalcemia, and renal insufficiency related to the proliferation of monoclonal plasma cells; and a proportion of plasma cells in the bone marrow of 10 percent or less.
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In large referral centers, half the patients with a monoclonal gammopathy have MGUS, whereas only 15 to 20 percent have multiple myeloma.
MGUS . . .
Elevated immunoglobulin free light chain (FLC) level and abnormal FLC ratio are commonly seen in multiple myeloma (MM) and have prognostic implications. We hypothesized that presence of immunoglobin ...heavy chain (IgH) translocations leads to unbalanced production of light chains and more extreme abnormalities of FLC, and may explain the prognostic value of FLC. We studied 314 patients with newly diagnosed MM enrolled in a phase III trial, in whom results of fluorescence in situ hybridization testing and data on serum FLC levels were available. Cytogenetic analyses and FLC estimates were performed on stored samples and results were correlated with clinical data. The median ratio (FLC ratio) and the absolute difference (FLC diff) between the involved and uninvolved FLC were higher among those with IgH translocations, especially t(14;16). In multivariate analysis, the prognostic value of FLC estimates on progression-free and overall survival were independent of high-risk IgH translocations t(4;14) and t(14;16). A combination of the risk factors; either abnormal FLC estimate and/or the presence of high-risk IgH translocation, achieved better prognostic stratification. We conclude that patients with IgH translocations have higher FLC levels and abnormal ratios, but the prognostic effect of FLC is only partially explained by translocation status. A system including both these risk factors allows better prediction of outcome.
Alpha-1-antitrypsin (A1AT) deficiency disease results from mutations in the A1AT gene. Controversy exists in regards to treatment of heterozygous carriers of the S and Z deficiency alleles. ...Quantitation of allelic expression has not been possible with standard laboratory methods. Here we show that the recently described method for liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis of A1AT tryptic peptides can differentiate between mutated (S and Z) and wild-type (non-S and non-Z) proteins allowing for quantitation of circulating allelic expression in heterozygous patients.
Serum (244 M/M, 61 M/Z, and 63 M/S) was combined with isotopically labeled peptide standards, digested with trypsin, and quantitated by LC-MS/MS. Total and allele-specific A1AT quantitation was performed by comparison of peptide peak height ratios to a standard curve for each peptide. Linear regression was used to compare results and central 95(th) percentile intervals were calculated using parametric analysis.
Quantitation of circulating wild-type A1AT based on the proteotypic and allelic (non-S and non-Z) peptides was validated in M/M patients. Proteotypic peptide concentrations correlated linearly with quantitation by non-Z and non-S peptides slopes (Spearman correlation coefficient) of 1.09 (0.89) and 0.98 (0.80), respectively. Allele-specific quantitation showed significant differences in wild-type protein expression in M/Z and M/S patients. Although average total A1AT concentration was lower for M/Z patients, the percentage of wild-type protein in M/Z patients was significantly higher at 82 % (55- > 95 %) compared to 63 % (43-83 %) for M/S heterozygotes. In a cohort of M/Z patients with sufficient total A1AT (≥80 mg/dL), half had insufficient wild-type protein that could have clinical implications for pulmonary dysfunction.
For the first time, a method to quantitate A1AT allele protein expression is described. Given the wide range of circulating wild-type protein observed in heterozygous patients, this method has the potential to reveal correlations between allele concentration and development and/or severity of clinical symptoms.
The detection of monoclonal free light chains (FLCs) is an important diagnostic aid for a variety of monoclonal gammopathies and is especially important in light-chain diseases, such as light-chain ...myeloma, primary systemic amyloidosis, and light-chain-deposition disease. These diseases are more prevalent in the elderly, and assays to detect and quantify abnormal amounts of FLCs require reference intervals that include elderly donors.
We used an automated immunoassay for FLCs and sera from a population 21-90 years of age. We used the calculated reference and diagnostic intervals to compare FLC results with those obtained by immunofixation (IFE) to detect low concentrations of monoclonal kappa and lambda FLCs in the sera of patients with monoclonal gammopathies.
Serum kappa and lambda FLCs increased with population age, with an apparent change for those >80 years. This trend was lost when the FLC concentration was normalized to cystatin C concentration. The ratio of kappa FLC to lambda FLC (FLC K/L) did not exhibit an age-dependent trend. The diagnostic interval for FLC K/L was 0.26-1.65. The 95% reference interval for kappa FLC was 3.3-19.4 mg/L, and that for lambda FLC was 5.7-26.3 mg/L. Detection and quantification of monoclonal FLCs by nephelometry were more sensitive than IFE in serum samples from patients with primary systemic amyloidosis and light-chain-deposition disease.
Reference and diagnostic intervals for serum FLCs have been developed for use with a new, automated immunoassay that makes the detection and quantification of monoclonal FLCs easier and more sensitive than with current methods. The serum FLC assay complements IFE and allows quantification of FLCs in light-chain-disease patients who have no detectable serum or urine M-spike.
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