Graham P. Mead

Serum test for assessment of patients with Bence Jones myeloma

Bence Jones protein in urine (immunoglobulin free-light-chains) is characteristic of light-chain multiple myeloma. We aimed to compare a quantitative immunoassay for serum free-light-chains with urine tests. Of 224 patients with light-chain myeloma tested at entry to clinical trials, all were correctly identified from serum samples. During monitoring of 82 patients, changes in serum and urine free-light-chains corresponded, but urine became negative for free-light-chains in 26 patients, whereas it remained abnormal in serum in 73 patients. Serum assays could replace Bence Jones protein urine tests for patients with light-chain multiple myeloma.

Efficient Removal of Immunoglobulin Free Light Chains by Hemodialysis for Multiple Myeloma: In Vitro and In Vivo Studies

Of patients with newly diagnosed multiple myeloma, approximately 10% have dialysis-dependent acute renal failure, with cast nephropathy, caused by monoclonal free light chains (FLC). Of these, 80 to 90% require long-term renal replacement therapy. Early treatment by plasma exchange reduces serum FLC concentrations, but randomized, controlled trials have shown no evidence of renal recovery. This outcome can be explained by the low efficiency of the procedure. A model of FLC production, distribution, and metabolism in patients with myeloma indicated that plasma exchange might remove only 25% of the total amount during a 3-wk period. For increasing FLC removal, extended hemodialysis with a protein-leaking dialyzer was used. In vitro studies indicated that the Gambro HCO 1100 dialyzer was the most efficient of seven tested. Model calculations suggested that it might remove 90% of FLC during 3 wk. This dialyzer then was evaluated in eight patients with myeloma and renal failure. Serum FLC reduced by 35 to 70% within 2 hr, but reduction rates slowed as extravascular re-equilibration occurred. FLC concentrations rebounded on successive days unless chemotherapy was effective. Five additional patients with acute renal failure that was caused by cast nephropathy then were treated aggressively, and three became dialysis independent. A total of 1.7 kg of FLC was removed from one patient during 6 wk. Extended hemodialysis with the Gambro HCO 1100 dialyzer allowed continuous, safe removal of FLC in large amounts. Proof of clinical value now will require larger studies.

Quantitative Assessment of Serum and Urinary Polyclonal Free Light Chains in Patients with Chronic Kidney Disease

BACKGROUND AND OBJECTIVES Monoclonal free light chains (FLC) frequently cause kidney disease in patients with plasma cell dyscrasias. Polyclonal FLC, however, have not been assessed in patients with chronic kidney disease (CKD) yet could potentially play an important pathologic role. This study describes for the first time polyclonal FLC in patients with CKD. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS A sensitive, quantitative immunoassay was used to analyze serum and urinary polyclonal FLC in 688 patients with CKD of various causes. RESULTS Serum kappa and lambda FLC concentrations increased progressively with CKD stage (both P < 0.001) and strongly correlated with markers of renal function, including cystatin-C (kappa: R = 0.8, P < 0.01; and lambda: R = 0.79, P < 0.01). Urinary FLC concentrations varied significantly between disease groups (kappa: P < 0.001; lambda: P < 0.005) and also rose significantly with increasing CKD stage (both FLC P < 0.0001). Urinary FLC concentrations were positively correlated with their corresponding serum concentration (kappa: R = 0.63; lambda: R = 0.65; both P < 0.001) and urinary albumin creatinine ratio (kappa: R = 0.58; lambda: R = 0.65; both P < 0.001). The proportion of patients with abnormally high urinary FLC concentrations rose with both the CKD stage and the severity of albuminuria. CONCLUSIONS This study demonstrates significant abnormalities of serum and urinary polyclonal FLC in patients with CKD. These data provide the basis for studies that assess the contribution of polyclonal FLC to progressive renal injury and systemic inflammation in patients with kidney disease.

Serum free light chains for monitoring multiple myeloma.

Monoclonal immunoglobulin free light chains (FLC) are found in the serum and urine of patients with a number of B-cell proliferative disorders, including multiple myeloma. Automated immunoassays, which can measure FLC in serum, are useful for the diagnosis and monitoring of light chain (AL) amyloidosis, Bence Jones myeloma and non-secretory myeloma patients. We report the results of a study investigating the utility of serum FLC measurements in myeloma patients producing monoclonal intact immunoglobulin proteins. FLC concentrations were measured in presentation sera from 493 multiple myeloma patients with monoclonal, intact immunoglobulin proteins. Serial samples were assayed from 17 of these patients and the FLC measurements were compared with other disease markers. Serum FLC concentrations were abnormal in 96% of patients at presentation. FLC concentrations fell more rapidly in response to treatment than intact immunoglobulin G (IgG) and showed greater concordance with serum beta2 microglobulin concentrations and bone marrow plasma cell assessments. It was concluded that serum FLC assays could be used to follow the disease course in nearly all multiple myeloma patients. In addition, because of their short serum half-life, changes in serum FLC concentrations provide a rapid indication of the response to treatment.Prior studies have demonstrated the utility of serum free light chains (FLC) in the diagnosis and monitoring of non-secretory (Drayson et al, 2001) and light chain myeloma (LCMM) (Bradwell et al, 2003). Mead et al (2004) have also suggested a role in myelomas that produce an intact immunoglobulin paraprotein (IIMM), where 96% of patients had an abnormal FLC ratio and/or monoclonal FLC concentration at diagnosis and it was concluded that serum FLC assays could be used to follow the disease course in nearly all multiple myeloma patients. We have reservations, however, regarding the broader application of FLC monitoring to patients with IIMM, in particular to the use of the FLC assay in monitoring for disease relapse post-autologous stem cell transplantation. We assessed whether the serum kappa to lambda (K/L) FLC ratio might be an early predictor of disease progression in patients with IIMM following autologous stem cell transplantation. Sera of patients with IIMM or LCMM who underwent autologous transplantation and were in complete remission or plateau phase were analysed. The FLC concentration was measured using a kit assay (The Binding Site Ltd, Birmingham, UK) and the Immage (Beckman Coulter, Brea, CA, USA) protein system. Monoclonal paraprotein was detected by serum protein electrophoresis (Beckman Coulter) and/or immunofixation (IFE). Myeloma response and relapse were defined according to international criteria (Bladé et al, 1998). Thirty-four patients were monitored post-transplant, on an average bimonthly, for a median of 16 months (range, 3–36 months). K/L FLC ratios were within the manufacturer’s reference interval for IIMM and LCMM patients in complete remission (0Æ41–1Æ59; n 1⁄4 15) except for one LCMM patient (K/L ratio 0Æ15) with no Bence Jones protein detected on IFE and 2% polyclonal plasma cells on bone marrow biopsy. Seventy-two per cent (13/18) of IIMM and LCMM patients in plateau phase (i.e. residual serum paraprotein ranging from <1 to 19 g/l or trace Bence Jones proteinuria) had a normalised FLC ratio (0Æ39–1Æ49) with four patients having abnormal ratios (0Æ16, 0Æ23, 0Æ24, 3Æ4, 5Æ5). Eleven patients with IIMM have relapsed. Whereas the FLC ratio and monoclonal FLC concentration have been reported to reflect changes in disease progression in LCMM (Bradwell et al, 2003), we did not observe the same correlation in IIMM (Table I). Of 11 relapsed IIMM patients, four had persisting normal FLC concentrations and ratios, despite rising paraprotein concentrations of 10–36 g/l and abnormal bone marrow biopsy (plasma cells 9–100%). In two other patients, increasing paraprotein concentration (IgA lambda 1Æ7–23 g/l; IgG kappa 11–27 g/l) preceded increasing monoclonal lambda FLC concentration (14–35 mg/l, ratio 0Æ96–0Æ29) and kappa FLC concentration (60–75 mg/l, ratio 5Æ5–11Æ9) by 8 and 4 months respectively. In another, increasing lambda FLC (40–179 mg/l; ratio 0Æ49–0Æ05) preceded an increase in paraprotein (19–31 g/l) by 11 months, and in four others, serum paraprotein and monoclonal FLC concentration increased simultaneously. Thus, 55% (6/11) of our transplanted group failed to give an abnormal ratio or elevated FLC concentration at or prior to disease relapse. Our data suggest that serum FLC measurement may not be useful as an early predictor of disease reoccurrence compared with the serum paraprotein in patients with IIMM posttransplantation. Systematic study of the role of FLC monitoring needs to occur in the context of larger prospective studies before it is routinely applied to the monitoring of patients with IIMM.

Serum free light chain measurement aids the diagnosis of myeloma in patients with severe renal failure.

BackgroundMonoclonal free light chains (FLCs) frequently cause rapidly progressive renal failure in patients with multiple myeloma. Immunoassays which provide quantitative measurement of FLCs in serum, have now been adopted into screening algorithms for multiple myeloma and other lymphoproliferative disorders. The assays indicate monoclonal FLC production by the presence of an abnormal κ to λ FLC ratio (reference range 0.26–1.65). Previous work, however, has demonstrated that in patients with renal failure the FLC ratio can be increased above normal with no other evidence of monoclonal proteins suggesting that in this population the range should be extended (reference range 0.37–3.1). This study evaluated the diagnostic sensitivity and specificity of the immunoassays in patients with severe renal failure.MethodsSera from 142 patients with new dialysis-dependent renal failure were assessed by serum protein electrophoresis (SPE), FLC immunoassays and immunofixation electrophoresis. The sensitivity and specificity of the FLC ratios published reference range was compared with the modified renal reference range for identifying patients with multiple myeloma; by receiver operating characteristic curve analysis.ResultsForty one patients had a clinical diagnosis of multiple myeloma; all of these patients had abnormal serum FLC ratios. The modified FLC ratio range increased the specificity of the assays (from 93% to 99%), with no loss of sensitivity. Monoclonal FLCs were identified in the urine from 23 of 24 patients assessed.ConclusionMeasurement of serum FLC concentrations and calculation of the serum κ/λ ratio is a convenient, sensitive and specific method for identifying monoclonal FLC production in patients with multiple myeloma and acute renal failure. Rapid diagnosis in these patients will allow early initiation of disease specific treatment, such as chemotherapy plus or minus therapies for direct removal of FLCs.

Use of Nonclonal Serum Immunoglobulin Free Light Chains to Predict Overall Survival in the General Population

OBJECTIVE To determine whether the free light chain (FLC) assay provides prognostic information relevant to the general population. METHODS After excluding persons with a known plasma cell disorder, we studied 15,859 Olmsted County, Minnesota, residents 50 years or older in whom unmasked data and samples for FLC testing were available. Baseline information was obtained between March 13, 1995, and November 21, 2003, and follow-up status and cause of death were identified through June 30, 2009. The κ and λ FLC sum (Σ FLC) was evaluated for its ability to predict overall survival. Specific causes of death were also investigated. RESULTS In 158,003 person-years of follow-up, 4348 individuals died. A high Σ FLC was significantly predictive of worse overall survival; the risk ratio for death for those with the highest decile of Σ FLC (ie, ≥ 4.72 mg/dL) was 4.4 (95% confidence interval, 4.1-4.7) relative to the remaining study participants. Multivariate analyses demonstrated that this excess risk of death was independent of age, sex, and renal insufficiency, with a corrected risk ratio of 2.1 (95% confidence interval, 1.9-2.2). The increased mortality was not restricted to any particular cause of death because the observed-to-expected risk of death from most causes was significantly higher among those individuals with an antecedent Σ FLC of 4.72 mg/dL or higher, which is near the upper limit of normal for the test. CONCLUSION A nonclonal elevation of Σ FLC is a significant predictor of worse overall survival in the general population of persons without plasma cell disorders.

Serum Free‐Light Chain Removal by High Cutoff Hemodialysis: Optimizing Removal and Supportive Care

In multiple myeloma the predominant cause of irreversible renal failure is cast nephropathy, secondary to excess kappa or lambda serum free light chains (FLCs). These molecules are efficiently cleared by hemodialysis (HD) using the Gambro HCO 1100 dialyzer. To optimize the removal of FLCs by this dialyzer we have studied the effect of dialyzers in series, dialyzer change, and hemodiafiltration in 14 patients with multiple myeloma and renal failure. The clearance rates of both kappa FLCs and lambda FLCs were significantly increased on two dialyzers from 19 (7.3-34)-15.3 (9-28) mL/min to 47 (17-79)-35.5 (20-57) mL/min, respectively. Clearance rates of both FLCs decreased over the course of the dialysis sessions (both P < 0.001). Changing the dialyzer during a HD session increased lambda FLC clearance rates (22.5 [6-41] to 37.6 [9-52] mL/min; P < 0.001) and decreased kappa FLC clearance rates (39.6 [9-72] to 19 [8-59] mL/min; P < 0.003). Ultrafiltration during HD increased the clearance rates of kappa FLCs (R 0.52, P < 0.01) but not lambda FLCs (R -0.25; P < 0.076). Hemodiafiltration increased the clearance rates of both kappa (19 [SD 6.8] to 32 [SD 9.8] mL/min) and lambda FLCs (15 [SD 7.8] to 20 [SD 7.7] mL/min). Albumin replacement requirements for 8 h of HD increased from 12 g for a single dialyzer to 45 g for two dialyzers in series (P < 0.001). Different protocols are required to optimize the removal of kappa and lambda FLCs in patients with myeloma and renal failure.

Abnormal serum free light chain ratios are associated with poor survival and may reflect biological subgroups in patients with chronic lymphocytic leukaemia.

The measurement of immunoglobulin serum free light chains (sFLC) has prognostic significance in plasma cell dyscrasias but its role in chronic lymphocytic leukaemia (CLL) is unknown. This retrospective study from three UK hospitals analysed sFLC in 181 untreated/pre‐treatment CLL patients and 78 treated CLL patients, with samples taken later in their disease. An abnormal sFLC ratio was significantly associated with poor overall survival for the 181 untreated/pre‐treatment patients (P = 0·0001) and for all patients (P = 0·002), irrespective of cause of death. Using multivariate analysis (n = 194), four independent prognostic variables for overall survival were identified namely Zap‐70 (P = 0·0001), β2M (P = 0·01), IGHV mutation status (P = 0·017) and an abnormal sFLC ratio (P = 0·024). For CLL patients with unmutated IGHV genes, elevated κ/λ ratios were adversely prognostic. For patients with mutated IGHV genes, reduced κ/λ ratios were adversely prognostic and associated with the poor prognostic IGHV3‐21, IGHV3‐48 and IGHV3‐53 subgroups, suggesting an abnormal sFLC ratio may reflect biological subgroups within CLL. Abnormal sFLC ratios need to be studied prospectively in CLL patients and the biological rationale for their abnormality investigated.

Quantitative assessment of serum and urinary polyclonal free light chains in patients with type II diabetes: an early marker of diabetic kidney disease?

Objective: Free light chains (FLCs) are bi-products of normal immunoglobulin synthesis and are predominately removed from the circulation by the kidneys. This study assessed polyclonal FLCs as a novel biomarker of early diabetic kidney disease. Research design/methods: Serum and urinary FLCs were assessed by the immunoassay Freelite, in white and South-Asian patients with type II diabetes recruited from the United Kingdom Asian Diabetes Study. Results: The incidence of monoclonal proteins in this diabetic population was 1.9%. Type II diabetic patients had significantly raised concentrations of serum polyclonal FLCs before overt renal impairment developed (p < 0.001). Both kappa and lambda FLCs correlated with all tested markers of renal function; in particular cystatin-C: Spearmans coefficient (R) = 0.55 (p < 0.01) and R = 0.56 (p < 0.01), respectively. The South-Asian diabetic patients had higher serum polyclonal FLCs than Caucasian diabetic patients and this was independent of renal function. Urinary FLCs concentrations were raised in diabetic patients (p < 0.001). The majority (68%) of diabetic patients with normal urinary albumin:creatinine ratios (ACRs) had abnormal urinary FLC:creatinine ratios. Both kappa and lambda FLC concentrations correlated with urinary ACR: R = 0.32, p < 0.01 and R = 0.25, p < 0.01 respectively. Conclusions: Type II diabetic patients can have significantly raised concentrations of serum and urinary polyclonal FLCs before overt renal disease occurs. These novel findings provide the basis for future studies to assess whether polyclonal FLCs could provide a useful tool for early diagnosis of diabetic kidney disease.

Serum free light chain immunoassays and their clinical application

Abstract Measurement of urine free light chains (flc) is important for assessing monoclonal plasma cell diseases. However, since the kidneys metabolize large amounts of flc, urine concentrations may not accurately reflect plasma cell synthesis. From a theoretical viewpoint, serum measurements would be preferable, just as blood glucose measurements are preferable to urine measurements for managing patients with diabetes mellitus. Unfortunately, the development of satisfactory serum flc immunoassays has been hampered by the lack of specific, high-affinity antisera. Recent publications indicate that this situation has now changed. Serum flc have been quantified using routine clinical laboratory instruments and have produced useful diagnostic results in several diseases. Thus, 100% of patients with light-chain multiple myeloma, 75% of patients with nonsecretory myeloma and more than 95% of patients with primary amyloidosis could be diagnosed using serum flc assays. This improvement in disease detection rates and the potential for superior disease monitoring may obviate the need for urine flc tests in most patients with monoclonal plasma cell diseases.