Colin A. Hutchison

Monoclonal gammopathy of renal significance: when MGUS is no longer undetermined or insignificant

Multiple myeloma is the most frequent monoclonal gammopathy to involve the kidney; however, a growing number of kidney diseases associated with other monoclonal gammopathies are being recognized. Although many histopathologic patterns exist, they are all distinguished by the monoclonal immunoglobulin (or component) deposits. The hematologic disorder in these patients is more consistent with monoclonal gammopathy of undetermined significance (MGUS) than with multiple myeloma. Unfortunately, due to the limitations of the current diagnostic schema, they are frequently diagnosed as MGUS. Because treatment is not recommended for MGUS, appropriate therapy is commonly withheld. In addition to end-stage renal disease, the persistence of the monoclonal gammopathy is associated with high rates of recurrence after kidney transplantation. Preservation and restoration of kidney function are possible with successful treatment targeting the responsible clone. Achievement of hematologic complete response has been shown to prevent recurrence after kidney transplantation. There is a need for a term that properly conveys the pathologic nature of these diseases. We think the term monoclonal gammopathy of renal significance is most helpful to indicate a causal relationship between the monoclonal gammopathy and the renal damage and because the significance of the monoclonal gammopathy is no longer undetermined.

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.

European trial of free light chain removal by extended haemodialysis in cast nephropathy (EuLITE): A randomised control trial

BackgroundRenal failure is a frequent complication of multiple myeloma and when severe is associated with a greatly increased morbidity and mortality. The principal cause of severe renal failure is cast nephropathy, a direct consequence of high concentrations of monoclonal free light chains (FLCs) in patients sera. FLC removal by extended haemodialysis, using a high cut-off dialyser, has recently been described as a novel therapeutic option.MethodsThe EU ropean trial of free LI ght chain removal by exTE nded haemodialysis in cast nephropathy (EuLITE) trial is a prospective, randomised, multicentre, open label clinical trial to investigate the clinical benefits of FLC removal haemodialysis in patients with cast nephropathy, dialysis dependent acute renal failure and de novo multiple myeloma. Recruitment commenced in May 2008. In total, 90 patients will be recruited. Participants will be randomised, centrally, upon enrolment, to either trial chemotherapy and FLC removal haemodialysis or trial chemotherapy and standard high flux haemodialysis. Trial chemotherapy consists of bortezomib, doxorubicin and dexamethasone. FLC removal haemodialysis is undertaken with two Gambro HCO 1100 dialysers in series using an intensive treatment schedule. The primary outcome for the study is independence of dialysis at 3 months. Secondary outcomes are: duration of dialysis, reduction in serum FLC concentrations; myeloma response and survival.HypothesisFLC removal haemodialysis will increase the rate of renal recovery in patients with severe renal failure secondary to cast nephropathy in de novo multiple myeloma.Trial registrationISRCTN45967602

Immunoglobulin free light chain levels and recovery from myeloma kidney on treatment with chemotherapy and high cut-off haemodialysis

BACKGROUNDnTo determine the efficacy of immunoglobulin free light chain (FLC) removal by high cut-off haemodialysis (HCO-HD) as an adjuvant treatment to chemotherapy for patients with acute kidney injury complicating multiple myeloma (MM).nnnMETHODSnSixty-seven patients with dialysis-dependent renal failure secondary to MM were treated with HCO-HD and chemotherapy.nnnRESULTSnThe population was predominantly male (62.7%) with new presentation MM (75%) and did not have a history of chronic kidney disease (84%). The mean serum creatinine at presentation was 662 (SD = 349) μmol/L and of the 56.7% of patients who had a renal biopsy, 86.7% had cast nephropathy as the principal diagnosis. Eighty-five percent of patients were treated with a chemotherapy regime consisting of dexamethasone in combination with a novel agent (bortezomib or thalidomide). The median number of HCO-HD sessions was 11 (range 3-45), 97% received an extended dialysis regime. Seventy-six percent of the population had a sustained reduction in serum FLC concentrations by Day 12, of these 71% subsequently became independent of dialysis. In total, 63% of population became independent of dialysis. Factors which predicted independence of dialysis were the degree of FLC reduction at Days 12 (P = 0.002) and 21 (P = 0.005) and the time to initiating HCO-HD (P = 0.006).nnnCONCLUSIONnThe combination of extended HCO-HD and chemotherapy resulted in sustained reductions in serum FLC concentrations in the majority of patients and a high rate of independence of dialysis.

The biology of immunoglobulin free light chains and kidney injury

Kidney injury caused by immunoglobulin free light chains (FLCs) in the setting of plasma cell dyscrasias is common and associated with increased morbidity and mortality. All compartments of the kidney may be affected, from the glomerulus to the tubulointerstitium, in a wide variety of disease patterns. Here, we review our current knowledge of the biological effects of FLCs and the mechanisms that lead to kidney injury.

High Cut-off Dialysis Membranes: Current Uses and Future Potential

The removal of larger uremic toxins by conventional dialysis membranes is restricted by their molecular weight cut-offs. The recent availability of a new generation of hemodialysis membranes with molecular weight cut-offs closer to that of the native kidney (65 kDa) has led to work assessing their potential utility across several different clinical scenarios. Initially designed to remove proinflammatory cytokines in patients with severe sepsis syndrome, clinicians are now using these membranes for the treatment of myeloma kidney and rhabdomyolysis. Further early pilot studies have demonstrated a potential utility for the removal of larger middle molecules in the population with end-stage renal failure. The purpose of this review was to summarize the current evidence base for the use of high cut-off hemodialysis membranes and discuss their future clinical relevance.

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.

The Incidence of Major Hemorrhagic Complications After Renal Biopsies in Patients with Monoclonal Gammopathies

BACKGROUND AND OBJECTIVESnMonoclonal gammopathies frequently cause renal disease, but they may be an incidental finding. Assessment of renal pathology in the context of renal dysfunction and a monoclonal gammopathy therefore serves as a useful diagnostic tool and, in addition, provides prognostic information. There is, however, a theoretical risk of increased hemorrhagic complications from renal biopsies in this setting. The purpose of this study was to determine the incidence of significant hemorrhagic complications after renal biopsies in patients with monoclonal gammopathies.nnnDESIGN, SETTING, PARTICIPANTS, & MEASUREMENTSnThe case notes of 1993 unselected patients from four teaching hospitals within the United Kingdom who underwent native or transplant renal biopsies between 1993 and 2008 were reviewed. Subjects were categorized as having a monoclonal gammopathy or not, and the incidence of major hemorrhagic complications between groups was compared.nnnRESULTSnIn total, 74 (3.7%) patients (native and transplant biopsies) had a major hemorrhagic complication. One hundred forty-eight subjects with a monoclonal gammopathy were identified. The complication rate in this group was 4.1% compared with 3.9% in the control population (native biopsies only; P = 0.88).nnnCONCLUSIONSnIn the population studied, the rate of major hemorrhagic complications after percutaneous renal biopsy was not significantly greater in patients with a monoclonal gammopathy.

Differential progression of renal scarring and determinants of late renal recovery in sustained dialysis dependent acute kidney injury secondary to myeloma kidney

Background Most cases of dialysis-dependent acute kidney injury due to myeloma cast nephropathy do not recover renal function. Renal biopsy typically shows cast formation, direct tubular injury and interstitial inflammation caused by nephrotoxic monoclonal free light chains (FLC). Established scarring at presentation is rarely severe. There is little data on in situ evolution of renal injury. Aims To conduct a detailed histological study of four patients with cast nephropathy. Methods Cast nephropathy was confirmed by renal biopsy. Treatment consisted of chemotherapy and high cut-off dialysis to maximise extracorporeal removal of FLC and reduce renal toxicity. All four patients remained dialysis dependent at 6 weeks, at which time they underwent a further biopsy. Results Three patients achieved independence from dialysis. Six-week biopsies showed differential changes in chronic damage from no progression, to accelerated progression of scarring from 10% to 42%, despite a rapid and sustained fall in FLC in all patients. In three patients there was a major reduction in intratubular cast numbers; these patients subsequently recovered renal function. In one patient who continued to have high cast formation at 6u2005weeks there was no subsequent renal recovery. Conclusions Some FLC clones can promote rapid renal scarring. Significant reductions in cast formation on repeat biopsy may identify the potential for late renal recovery. Early diagnosis and treatment may prove crucial in determining renal recovery. Patients who have not recovered renal function after a period of treatment may be usefully reassessed by repeat biopsy for quantitative analysis of chronic damage and cast numbers.

A modeled economic evaluation of sevelamer for treatment of hyperphosphatemia associated with chronic kidney disease among patients on dialysis in the United Kingdom

Abstract Objective: There is limited information regarding the cost-effectiveness of sevelamer for the treatment of hyperphosphatemia in chronic kidney disease (CKD) patients on dialysis in the UK. Using a UK National Health Service (NHS) perspective and final results of the Dialysis Clinical Outcomes Revisited (DCOR) study, an evaluation was performed to determine the cost-effectiveness of sevelamer compared to calcium-based phosphate binders for the first-line treatment of hyperphosphatemia in CKD patients on dialysis. Methods: A Markov model was developed to estimate life years, quality-adjusted life years (QALYs), costs, incremental cost per life year (LY) gained, and QALY gained. Treatment-specific overall survival up to 44 months, hospitalizations, and resource utilization were derived from the DCOR study. Survival was extrapolated to a lifetime horizon using Weibull regression analysis. Unit costs and utility estimates specific to the UK were obtained from the published literature. Sub-group analyses were conducted based on data reported from the DCOR study for increasing age cut-points. Outcomes and costs were modeled for a lifetime horizon. Results: In the base case analysis, the use of sevelamer resulted in a gain of ∼0.73 LYs and 0.44 QALYs per patient (discounted at 3.5% per year). Total per-patient costs were higher for sevelamer, resulting in an incremental cost of £22,157 per QALY gained and £13,427 per LY gained (in £2009). Increasingly favorable cost per QALY ratios were observed with increasing age cut-points, ranging from £15,864 for patients ≥45 to £13,296 for patients ≥65 years of age. Results were most sensitive to assumptions regarding overall survival and the inclusion of dialysis costs. Key limitations of the analysis included the use of non-UK trial data for survival and hospitalizations, and the exclusion of quality-of-life impacts associated with hospitalization. Conclusions: In CKD patients receiving dialysis, treatment of hyperphosphatemia with sevelamer offers good value for money compared with calcium-based binders.