Clinical specificity of two assays for immunoglobulin kappa and lambda free light chains.

OBJECTIVES: Free light chain (FLC) assays and the ratio of κ/λ are recommended for diagnosis, prognosis and monitoring of plasma cell dyscrasias (PCD). Limited data exists on FLC clinical specificity in patients diagnosed with other conditions. METHODS: We assessed the κ, λ, and κ/λ FLC ratio using the FreeLite assay and the Sebia FLC ELISA assay in 176 patients with clinical presentations of fatigue, anemia, polyclonal hypergammaglobulinemia, joint disorders, kidney disease and non PCD-cancers with no monoclonal protein observed on serum protein electrophoresis or MASS-FIX immunoglobulin isotyping. Manufacturer defined reference intervals (RI) and glomerular filtration rate (GFR) specific RI (renal RI) were utilized. RESULTS: For the κ/λ ratio, 68.7 % (121/176) of specimens on the FreeLite and 87.5 % (154/176) of specimens on the Sebia assay were within RI. For κ, 68.2 % (120/176) and 72.2 % (127/176) of results were outside RI for FreeLite and Sebia respectively. For λ, 37.5 % (66/176) and 84.1 % (148/176) of FreeLite and Sebia results were outside RI. With FreeLite and Sebia, patients with kidney disease (n=25) had the highest κ/λ ratios. 44 patients (25.0 %) had GFR <60 mL/min/BSA. When renal RI were applied, 13.6 % had a FLCr outside the renal RI with FreeLite, and 4.5 % with Sebia. CONCLUSIONS: In a cohort of patients with signs and symptoms suggestive of PCDs, but ultimately diagnosed with other conditions, Sebia FLC had improved clinical specificity relative to FreeLite, if one was using an abnormal κ/λ ratio as a surrogate for monoclonality.

Utilizing Mass Spectrometry to Detect and Isotype Monoclonal Proteins in Urine: Comparison to Electrophoretic Methods.

BACKGROUND: Matrix assisted laser desorption ionization time of flight mass spectrometry coupled to immune enrichment (MASS-FIX) as an alternative to serum immunofixation electrophoresis has demonstrated increased sensitivity in monoclonal protein (MP) detection with improved laboratory workflow. This study explored similar replacement of urine immunofixation electrophoresis (u-IFE) with urine MASS-FIX (u-MASS-FIX) by method comparison. METHODS: Residual urine (n = 1008) from Mayo Clinic patients with a known plasma cell disease were assayed neat by u-MASS-FIX analysis. Each sample was paired with the following: u-IFE, urine total protein, urine protein electrophoresis, serum κ/λ free light chain (LC) ratio (rFLC), and serum MASS-FIX (s-MASS-FIX). Analytical sensitivities were measured in pooled urine spiked with daratumumab. RESULTS: u-IFE and u-MASS-FIX had 91% agreement in determining the presence/absence of MPs (Cohen kappa = 0.8200). In discrepant cases, serum rFLC statistically aligned more closely with positive u-MASS-FIX cases than u-IFE. Patients positive by both s-MASS-FIX and u-MASS-FIX had matching MP masses (±20 daltons) in 94% of cases. The u-MASS-FIX spectra further identified κ/λ LC fragments and glycosylated LCs not appreciated on u-IFE. The unconcentrated u-MASS-FIX limit of detection of 0.156 mg/mL was determined equivalent to 100× concentrated u-IFE. CONCLUSION: u-MASS-FIX is a reliable alternative to u-IFE with the added benefits of LC glycosylation detection and MP mass tracking between serum and urine. Furthermore, u-MASS-FIX is performed using neat urine. Eliminating the need to concentrate urine for u-IFE has potential to increase productivity by decreasing labor minutes per test.

The characteristics of seronegative and seropositive non-hepatitis-associated cryoglobulinemic glomerulonephritis.

The clinicopathologic characteristics and long-term outcome of non-hepatitis-associated cryoglobulinemic glomerulonephritis (CryoGN) are not well-defined and cases with undetectable serum cryoglobulin (seronegative CryoGN) have not been investigated. To resolve this, we retrospectively identified 81 patients with biopsy-proven non-hepatitis CryoGN, including 22 with seronegative CryoGN. The median age was 61 years and 76% presented with nephritic syndrome. A hematologic condition was found in 89% of patients, including monoclonal gammopathy of renal significance (65%) and symptomatic lymphoproliferative disorder (35%). In the seropositive group, 56% had type II, 29% type I, and 8% type III cryoglobulin. Extrarenal manifestations, mostly of skin, were present in 64% and were significantly less common in seronegative CryoGN. Glomerular deposits by immunofluorescence were IgM dominant (84%) and polytypic (70%) in the seropositive group, whereas 52% of seronegative cases had monotypic deposits (i.e., type I cryoglobulin). Ultrastructurally, the deposits were organized in 77% of cases. Substructure appearance significantly differed according to the type of CryoGN, forming most commonly short cylindrical structures in type II and other organized substructures in type I CryoGN. Most patients were treated with clone-directed therapy. On follow up (median 33 months), 77% had partial or complete remission, 10% reached kidney failure and 14% died. Predictors of kidney failure on univariate analysis were AKIN stage 3, positive rheumatoid factor and biclonal gammopathy at diagnosis. We conclude that most CryoGN cases (types I and II) are due to a hematologic condition and are associated with favorable outcome after clone-directed therapy. Seronegative CryoGN accounts for about a quarter of cases and is mostly a kidney-limited disease. Thus, further investigations are needed to unravel the pathophysiology of seronegative CryoGN.

Kidney Transplantation in Patients With Monoclonal Gammopathy of Renal Significance (MGRS)-Associated Lesions: A Case Series.

RATIONALE & OBJECTIVE: Data on kidney transplantation outcomes among patients with monoclonal gammopathy of renal significance (MGRS) are lacking. STUDY DESIGN: Case series of patients with MGRS, some of whom received clone-directed therapies before kidney transplantation. SETTING & PARTICIPANTS: 28 patients who underwent kidney transplantation from 1987 through 2016 after diagnosis with MGRS-associated lesions including light-chain deposition disease (LCDD), C3 glomerulopathy with monoclonal gammopathy (C3G-MG), and light-chain proximal tubulopathy (LCPT). FINDINGS: Of the 19 patients with LCDD, 10 were treated before kidney transplantation and 9 were treatment-naive. Among the treated patients with LCDD, 3 (30%) experienced histologic recurrence, 2 (20%) grafts failed, and 2 (20%) died during a median follow-up of 70 (range, 3-162) months after transplant. In the treatment-naive LCDD group, 8 (89%) had histologic recurrence, 6 (67%) grafts failed, and 4 (44%) patients died during a median follow-up of 60 (range, 35-117) months. Of the 5 patients who had a complete response before transplant, none died, and only 1 experienced graft failure, 162 months after transplant. Of 5 patients with C3G-MG, 3 were treatment-naive before transplant. Both patients who were treated before transplant had histologic recurrence, and 1 experienced graft failure and died. Among the 3 patients with treatment-naive C3G-MG, histologic recurrence occurred in all, and graft loss and death were observed in 2 and 1, respectively. In the LCPT group (n=4), histologic recurrence was observed in all 3 patients who did not receive clone-directed therapies before transplant, and 2 of these patients died, 1 with a functioning kidney. The 1 patient with LCPT who received therapy before transplant did not have histologic recurrence or graft loss and survived. LIMITATIONS: Small sample size, nonstandardized clinical management, retrospective design. CONCLUSIONS: Recurrence is very common in all MGRS-associated lesions after kidney transplant. Achieving a complete hematologic response may reduce the risks of recurrence, graft loss, and death. More studies are needed to determine the effects of hematologic response on outcomes for each MGRS-associated lesion.

A study from The Mayo Clinic evaluated long-term outcomes of kidney transplantation in patients with immunoglobulin light chain amyloidosis.

Longer survival using modern therapies has increased the number of patients with immunoglobulin light-chain amyloidosis receiving kidney transplantation. We evaluated 60 patients with immunoglobulin light chain amyloidosis who underwent kidney transplantation based on their hematologic response for outcomes of death, graft failure, and complications. Patient hematologic responses (light-chain in blood or urine) prior to kidney transplantation were three patients had no response, five had a partial response, six had a very good partial response, 37 had a complete response, and nine were treatment-naive patients (never treated for this disorder). After transplantation, seven of nine treatment-naive patients achieved a complete response. The median follow-up for the entire transplant cohort was 61 months. The estimated median overall survival from the time of kidney transplantation was 123 months for the entire group. Median overall survival was not reached for the very good partial response plus complete response groups, it was 47 months for no response plus partial response groups, and 117 months for the treatment-naive group (all significantly different). Median overall survival of very good partial response was 81 months, while the median was not reached in the complete response group (no significant difference). The time to amyloid recurrence was significantly longer in complete response compared to very good partial response (median 181 vs 81 months). Death-censored graft survival at one- and five-years was 98.3%, and 95.8%, respectively for all groups. Of the 60 patients, three had allograft failure, 19 died with a functioning graft, and 13 had an amyloid recurrence. Thus, outcomes after kidney transplant in patients with immunoglobulin light-chain amyloidosis seem acceptable if a very good partial response or complete response is achieved either before or after transplantation.

Implications of detecting serum monoclonal protein by MASS-fix following stem cell transplantation in multiple myeloma.

Measurable residual disease (MRD) assessment by marrow-based next-generation flow cytometry (NGF) following autologous stem cell transplantation (ASCT) may lead to false-negative results due to patchy marrow involvement and extramedullary disease in patients with multiple myeloma. We assessed the value of simultaneous MRD evaluation with NGF and serum matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MASS-FIX). Of all 61 complete responders who were NGF-negative for MRD, around day-100 post ASCT, 59% were MASS-FIX-positive. At median follow-up of 26 months, 69% of MASS-FIX(+)/NGF(-) patients were alive and progression-free versus 96% of MASS-FIX(-)/NGF(-) patients, P = 0·02. MASS-FIX, a simple peripheral blood-based assay complements marrow-based NGF to accurately prognosticate patients with myeloma.

In from the cold: M-protein light chain glycosylation is positively associated with cold agglutinin titer levels.

BACKGROUND: Primary cold agglutinin disease (CAD) is a monoclonal antibody (M-protein) and complement-mediated chronic hemolytic disease process. Antibody glycosylation can play a role in both antibody half-life and complement fixation. Recently, M-protein light chain (LC) glycosylation has been shown to be associated with AL amyloidosis. We hypothesized that M-protein LC glycosylation is also associated with cold agglutinin (CA) titers and CA-mediated hemolysis. STUDY DESIGN AND METHODS: A cross-sectional study of patients undergoing CA titer evaluation underwent mass spectrometric analysis for M-proteins and M-protein LC glycosylation. A subset of serum samples also underwent evaluation for the ability to trigger cold hemolysis in vitro. M-protein and M-protein LC glycosylation rates were compared across CA titer groups, clinical diagnosis, direct antiglobulin testing (DAT) results, and cold in vitro hemolysis rates. RESULTS: Both M-protein and M-protein LC glycosylation rates significantly differed across CA titer groups with the highest rates in those with elevated CA titers. M-protein LC glycosylation occurred almost exclusively on IgM kappa M-proteins and was significantly associated with positive DAT results and a clinical diagnosis of CAD. Cold in vitro hemolysis was demonstrated in two patients who both had a CA titer of more than 512 but there was no significant association with CA titer group or M-protein LC glycosylation status. CONCLUSION: M-protein LC glycosylation is significantly associated with higher CA titer levels. Given the role that antibody glycosylation can play in antibody half-life and complement fixation, further studies are needed to clarify the effects of LC glycosylation within the context of CAD.

Automation and validation of a MALDI-TOF MS (Mass-Fix) replacement of immunofixation electrophoresis in the clinical lab.

Objectives: A matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS) method (Mass-Fix) as a replacement for gel-based immunofixation (IFE) has been recently described. To utilize Mass-Fix clinically, a validated automated method was required. Our aim was to automate the pre-analytical processing, improve positive specimen identification and ergonomics, reduce paper data storage and increase resource utilization without increasing turnaround time. Methods: Serum samples were batched and loaded onto a liquid handler along with reagents and a barcoded sample plate. The pre-analytical steps included: (1) Plating immunopurification beads. (2) Adding 10 µl of serum. (3) Bead washing. (4) Eluting the immunoglobulins (Igs), and reducing to separate the heavy and light Ig chains. The resulting plate was transferred to a second low-volume liquid handler for MALDI plate spotting. MALDI-TOF mass spectra were collected. Integrated in-house developed software was utilized for sample tracking, driving data acquisition, data analysis, history tracking, and result reporting. A total of 1,029 residual serum samples were run using the automated system and results were compared to prior electrophoretic results. Results: The automated Mass-Fix method was capable of meeting the validation requirements of concordance with IFE, limit of detection (LOD), sample stability and reproducibility with a low repeat rate. Automation and integrated software allowed a single user to process 320 samples in an 8 h shift. Software display facilitated identification of monoclonal proteins. Additionally, the process maintains positive specimen identification, reduces manual pipetting, allows for paper free tracking, and does not significantly impact turnaround time (TAT). Conclusions: Mass-Fix is ready for implementation in a high-throughput clinical laboratory.

Clinical features, laboratory characteristics and outcomes of patients with renal versus cardiac light chain amyloidosis.

This study evaluated the differences in clinical features of 1077 newly diagnosed AL amyloidosis patients with renal involvement (n = 229, 21%), both cardiac and renal involvement (n = 443, 41%) and cardiac involvement (n = 405, 38%). Significant differences in dFLC (difference in involved and uninvolved light chains) were noted (renal, both, cardiac median: 83, 234 and 349 mg/l, P < 0.001). The proportion of patients with ≥ 10% bone marrow plasma cells (BMPCs) was lowest in renal only patients: 44%, 57%, 64%, respectively, P < 0.001. In a multivariate linear regression model incorporating organ involvement type and BMPCs ≥10%, organ involvement was a significant predictor of dFLC (P < 0.001). Median overall survival (OS) across the three groups was 83 vs. 19 vs. 16 months (P < 0.001) in patients not undergoing transplant and 5-year OS in patients undergoing transplant was 90% vs. 75% vs. 64% (P = 0.007), respectively. In conclusion, renal involvement alone or renal + cardiac involvement in AL amyloidosis is associated with lower circulating light chain burden, which cannot be fully explained by BMPC burden alone. Increased sensitivity of the kidney to light chains, given significant interactions with the renal tubular system and secretion of modified light chain products may play a role in pathogenesis of renal AL amyloidosis and warrants further investigation.

Classification of Plasma Cell Disorders by 21 Tesla Fourier Transform Ion Cyclotron Resonance Top-Down and Middle-Down MS/MS Analysis of Monoclonal Immunoglobulin Light Chains in Human Serum.

The current five-year survival rate for systemic AL amyloidosis or multiple myeloma is ∼51%, indicating the urgent need for better diagnosis methods and treatment plans. Here, we describe highly specific and sensitive top-down and middle-down MS/MS methods owning the advantages of fast sample preparation, ultrahigh mass accuracy, and extensive residue cleavages with 21 telsa FT-ICR MS/MS. Unlike genomic testing, which requires bone marrow aspiration and may fail to identify all monoclonal immunoglobulins produced by the body, the present method requires only a blood draw. In addition, circulating monoclonal immunoglobulins spanning the entire population are analyzed and reflect the selection of germline sequence by B cells. The monoclonal immunoglobulin light chain FR2-CDR2-FR3 was sequenced by database-aided de novo MS/MS and 100% matched the gene sequencing result, except for two amino acids with isomeric counterparts, enabling accurate germline sequence classification. The monoclonal immunoglobulin heavy chains were also classified into specific germline sequences based on the present method. This work represents the first application of top/middle-down MS/MS sequencing of endogenous human monoclonal immunoglobulins with polyclonal immunoglobulins background.

Direct Detection of Monoclonal Free Light Chains in Serum by Use of Immunoenrichment-Coupled MALDI-TOF Mass Spectrometry.

BACKGROUND: Free light chain (FLC) quantification is the most analytically sensitive blood-based method commercially available to diagnose and monitor patients with plasma cell disorders (PCDs). However, instead of directly detecting monoclonal FLCs (mFLCs), FLC assays indirectly assess clonality based on quantifying κ and λ FLCs and determination of the к/λ FLC ratio. Often an abnormal FLC ratio is the only indication of a PCD, and confirmation by a direct method increases diagnostic confidence. The aim of this study was to develop an analytically sensitive method for direct detection of mFLCs. METHODS: Patient sera (n = 167) previously assessed by nephelometric FLC quantification and immunofixation electrophoresis (IFE) were affinity enriched for IgG, IgA, and total and free κ and λ light chains and subjected to MALDI-TOF MS. Relative analytical sensitivity of these methods was determined using serially diluted sera containing mFLCs. RESULTS: In sera with abnormal FLC ratios (n = 127), 43% of monoclonal proteins were confirmed by IFE, 57% by MALDI-TOF MS without FLC enrichment, and 87% with FLC enrichment MALDI-TOF MS. In sera with normal FLC ratios (n = 40), the FLC MALDI-TOF MS method identified 1 patient with an mFLC. Serial dilution and analysis of mFLC containing sera by IFE, nephelometry, and FLC MALDI-TOF MS demonstrated that FLC MALDI-TOF MS analysis had the highest analytical sensitivity. CONCLUSIONS: FLC immunoenrichment coupled to MALDI-TOF MS enables direct detection of mFLCs and significantly increases the confirmation of abnormal serum FLC ratios over IFE and MALDI-TOF MS without FLC enrichment, thereby providing added confidence for diagnosing FLC PCDs.

Accumulation of Gadolinium in Human Cerebrospinal Fluid after Gadobutrol-enhanced MR Imaging: A Prospective Observational Cohort Study.

Purpose To determine whether gadolinium accumulates within cerebrospinal fluid (CSF) in patients recently exposed to the macrocyclic agent gadobutrol and identify factors that may affect this accumulation. Materials and Methods In this prospective observational cohort study, gadolinium was quantified by using inductively coupled plasma mass spectrometry of CSF samples from patients who underwent gadobutrol-enhanced magnetic resonance (MR) imaging followed by lumbar puncture within 30 days (gadobutrol group) or patients who underwent lumbar puncture without history of gadolinium-enhanced MR imaging (control group). CSF total protein level of 35 mg/dL or lower was used as a surrogate marker of an intact blood-brain barrier (BBB). Associations between gadolinium CSF concentration and patient characteristics were examined by using log (e)-linear regression models. Results A total of 82 patients (68 in gadobutrol group, 14 in control group; 42 male and 40 female patients; median age, 47 years [interquartile range, 25-65 years]) were included in this study. Gadolinium was detected in the CSF of all 68 patients in the gadobutrol group (100% [95% confidence interval: 94.7, 100]; range, 0.2-1494 ng/mL). CSF total protein level higher than 35 mg/dL and patient age of at least 18 years were associated with higher gadolinium concentrations (estimate: 1.1, with standard error [SE] of 0.26 [P < .001] and 0.91, with SE of 0.37 [P = .02], respectively). Conclusion Intravenous administration of the macrocyclic agent gadobutrol results in gadolinium accumulation within the CSF, even in the setting of normal renal function and no BBB dysfunction.

Pharmacokinetics of rituximab and clinical outcomes in patients with anti-neutrophil cytoplasmic antibody associated vasculitis.

Objectives: To study the determinants of the pharmacokinetics (PK) of rituximab (RTX) in patients with ANCA-associated vasculitis (AAV) and its association with clinical outcomes. Methods: This study included data from 89 patients from the RTX in AAV trial who received the full dose of RTX (four weekly infusions of 375 mg/m2). RTX was quantified at weeks 2, 4, 8, 16 and 24, and summarized by computing the trapezoidal area under the curve. We explored potential determinants of the PK-RTX, and analysed its association with clinical outcomes: achievement of remission at 6 months, duration of B-cell depletion and time to relapse in patients who achieved complete remission. Results: RTX serum levels were significantly lower in males and in newly diagnosed patients, and negatively correlated with body surface area, baseline B-cell count and degree of disease activity. In multivariate analyses, the main determinants of PK-RTX were sex and new diagnosis. Patients reaching complete remission at month 6 had similar RTX levels compared with patients who did not reach complete remission. Patients with higher RTX levels generally experienced longer B-cell depletion than patients with lower levels, but RTX levels at the different time points and area under the curve were not associated with time to relapse. Conclusion: Despite the body-surface-area-based dosing protocol, PK-RTX is highly variable among patients with AAV, its main determinants being sex and newly diagnosed disease. We did not observe any relevant association between PK-RTX and clinical outcomes. The monitoring of serum RTX levels does not seem clinically useful in AAV.

CSF free light chain identification of demyelinating disease: comparison with oligoclonal banding and other CSF indexes.

BACKGROUND: Cerebrospinal fluid (CSF) used in immunoglobulin gamma (IgG) index testing and oligoclonal bands (OCBs) are common laboratory tests used in the diagnosis of multiple sclerosis. The measurement of CSF free light chains (FLC) could pose as an alternative to the labor-intensive isoelectric-focusing (IEF) gels used for OCBs. METHODS: A total of 325 residual paired CSF and serum specimens were obtained after physician-ordered OCB IEF testing. CSF kappa (cKFLC) and lambda FLC (cLFLC), albumin and total IgG were measured. Calculations were performed based on combinations of analytes: CSF sum of kappa and lambda ([cKFLC+cLFLC]), kappa-index (K-index) ([cKFLC/sKFLC]/[CSF albumin/serum albumin]), kappa intrathecal fraction (KFLCIF) {([cKFLC/sKFLC]-[0.9358×CSF albumin/serum albumin]^[0.6687×sKFLC]/cKFLC)} and IgG-index ([CSF IgG/CSF albumin]/[serum IgG/serum albumin]). RESULTS: Patients were categorized as: demyelination (n=67), autoimmunity (n=53), non-inflammatory (n=50), inflammation (n=38), degeneration (n=28), peripheral neuropathy (n=24), infection (n=13), cancer (n=11), neuromyelitis optica (n=10) and others (n=31). cKFLC measurement used alone at a cutoff of 0.0611 mg/dL showed >90% agreement to OCBs, similar or better performance than all other calculations, reducing the number of analytes and variables. When cases of demyelinating disease were reviewed, cKFLC measurements showed 86% clinical sensitivity/77% specificity. CONCLUSIONS: cKFLC alone demonstrates comparable performance to OCBs along with increased sensitivity for demyelinating diseases. Replacing OCB with cKFLC would alleviate the need for serum and CSF IgG and albumin and calculated conversions. cKFLC can overcome challenges associated with performance, interpretation, and cost of traditional OCBs, reducing costs and maintaining sensitivity and specificity supporting MS diagnosis.

Gadolinium Deposition in Human Brain Tissues after Contrast-enhanced MR Imaging in Adult Patients without Intracranial Abnormalities.

Purpose To determine whether gadolinium deposits in neural tissues of patients with intracranial abnormalities following intravenous gadolinium-based contrast agent (GBCA) exposure might be related to blood-brain barrier integrity by studying adult patients with normal brain pathologic characteristics. Materials and Methods After obtaining antemortem consent and institutional review board approval, the authors compared postmortem neuronal tissue samples from five patients who had undergone four to 18 gadolinium-enhanced magnetic resonance (MR) examinations between 2005 and 2014 (contrast group) with samples from 10 gadolinium-naive patients who had undergone at least one MR examination during their lifetime (control group). All patients in the contrast group had received gadodiamide. Neuronal tissues from the dentate nuclei, pons, globus pallidus, and thalamus were harvested and analyzed with inductively coupled plasma mass spectrometry (ICP-MS), transmission electron microscopy with energy-dispersive x-ray spectroscopy, and light microscopy to quantify, localize, and assess the effects of gadolinium deposition. Results Tissues from the four neuroanatomic regions of gadodiamide-exposed patients contained 0.1-19.4 µg of gadolinium per gram of tissue in a statistically significant dose-dependent relationship (globus pallidus: ρ = 0.90, P = .04). In contradistinction, patients in the control group had undetectable levels of gadolinium with ICP-MS. All patients had normal brain pathologic characteristics at autopsy. Three patients in the contrast group had borderline renal function (estimated glomerular filtration rate <45 mL/min/1.73 m2) and hepatobiliary dysfunction at MR examination. Gadolinium deposition in the contrast group was localized to the capillary endothelium and neuronal interstitium and, in two cases, within the nucleus of the cell. Conclusion Gadolinium deposition in neural tissues after GBCA administration occurs in the absence of intracranial abnormalities that might affect the permeability of the blood-brain barrier. These findings challenge current understanding of the biodistribution of these contrast agents and their safety. © RSNA, 2017.

Comparison of Gadolinium Concentrations within Multiple Rat Organs after Intravenous Administration of Linear versus Macrocyclic Gadolinium Chelates.

Purpose To compare gadolinium tissue concentrations of multiple linear and macrocyclic chelates in a rat model to better understand the scope and extent of tissue deposition following multiple intravenous doses of gadolinium-based contrast agent (GBCA). Materials and Methods In this Institutional Animal Care and Use Committee-approved study, healthy rats received 20 intravenous injections of 2.5 mmol gadolinium per kilogram (gadolinium-exposed group) or saline (control group) over a 26-day period. Unenhanced T1 signal intensities of the dentate nucleus were measured from magnetic resonance (MR) images obtained prior to GBCA injection and 3 days after final injection. Rat brain and renal, hepatic, and splenic tissues were harvested 7 days after final injection and subjected to inductively coupled plasma mass spectrometry and transmission electron microscopy for quantification and characterization of gadolinium deposits. Results Gadolinium deposition in brain tissue significantly varied with GBCA type (F = 31.2; P < .0001), with median concentrations of 0 µg gadolinium per gram of tissue (95% confidence interval [CI]: 0, 0.2) in gadoteridol-injected rats, 1.6 µg gadolinium per gram of tissue (95% CI: 0.9, 4.7) in gadobutrol-injected rats, 4.7 µg gadolinium per gram of tissue (95% CI: 3.5, 6.1) in gadobenate dimeglumine-injected rats, and 6.9 µg gadolinium per gram of tissue (95% CI: 6.2, 7.0) in gadodiamide-injected rats; a significant positive dose-signal intensity correlation was identified (ρ = 0.93; P < .0001). No detectable neural tissue deposition or MR imaging signal was observed in control rats (n = 6). Similar relative differences in gadolinium deposition were observed in renal, hepatic, and splenic tissues at much higher tissue concentrations (P < .0001). Gadolinium deposits were visualized directly in the endothelial capillary walls and neural interstitium in GBCA-injected rats, but not in control rats. Conclusion Tissue deposition of gadolinium was two- to fourfold higher following administration of the linear agents gadodiamide and gadobenate dimeglumine compared with the macrocyclic agents gadobutrol and gadoteridol. These findings suggest that organ tissue deposition is reduced but not eliminated following administration of macrocyclic GBCA chelates in lieu of linear chelates. © RSNA, 2017 Online supplemental material is available for this article.

Cryofibrinogen-Associated Glomerulonephritis.

Cryofibrinogen is an under-recognized cryoprotein. Cryofibrinogen is a cryoprecipitate that develops following plasma refrigeration, but does not occur in cold serum. People with cryofibrinogenemia may be asymptomatic, but this cryoprotein can be associated with thromboembolic disease, particularly affecting the skin. Kidney manifestations are relatively uncommon, but are likely underestimated. We describe clinical features and kidney biopsy results in 2 patients with cryofibrinogen-related kidney disease. Both patients presented with proteinuria and hematuria. One had significant cutaneous ulcers and palpable purpura. Kidney biopsy in both cases showed membranoproliferative glomerulonephritis with no immunoglobulin deposition. Weak segmental capillary wall fibrinogen staining was noted in glomeruli. Immunofluorescence studies following pronase digestion failed to reveal masked immunoglobulin deposits. Ultrastructural studies were distinctive and characterized by organized deposits of large-bore with multilayered tubular structures and fine fibrillary structures in a matrix. To confirm the composition of deposits, we extracted the cryoprecipitate from plasma of a patient and performed ultrastructural studies, which showed identical ultrastructural characteristics to those seen on the kidney biopsy. We also performed proteomic analysis of the cryoprecipitate that confirmed the presence of fibrinogen. Subsequent laboratory evaluation was positive for cryofibrinogen in both patients on multiple occasions. Appropriate therapy was instituted in both patients, which included prednisone, immunosuppressive therapy, and avoidance of cold exposure. In summary, we present clinical, kidney biopsy, and laboratory findings and the treatment and follow-up of cryofibrinogen-associated glomerulonephritis. Awareness of this entity will result in accurate diagnoses, appropriate investigation, and treatment.

The utility of MASS-FIX to detect and monitor monoclonal proteins in the clinic.

The detection and quantification of monoclonal-proteins (M-proteins) are necessary for the diagnosis and evaluation of response in plasma cell dyscrasias. Immunoglobulin enrichment-coupled with matrix-assisted laser desorption ionization time-of-flight mass-spectrometry (MASS-FIX) is a simple and inexpensive method to identify M-proteins, but its clinical generalizability has not yet been elucidated. We compared MASS-FIX to protein electrophoresis (PEL), serum/urine immunofixation-electrophoresis (IFE), and quantitative serum free-light chain (FLC) for the identification of M-proteins in different clinical diagnoses. Paired serum and urine samples from 257 patients were tested. There were six patients for whom s-IFE and FLC ratio were positive and serum MASS-FIX was negative, but when serum and urine MASS-FIX results were combined, only one patient with light chain-MGUS was missed. Serum/urine-MASS-FIX detected M-proteins in 18 patients with negative serum/urine-PEL/IFE and serum-FLC, 10 of whom had multiple myeloma or AL amyloidosis, who were mistakenly thought to have complete hematologic response by serum/urine-PEL/IFE and serum-FLC. Nearly half of the AL amyloidosis patients had atypical spectra, which may prove to be a clue to the diagnosis and pathogenesis of the disease. In conclusion, MASS-FIX has a comparable sensitivity with PEL/IFE/FLC methods and can help inform the clinical diagnosis.

Assessment of renal response with urinary exosomes in patients with AL amyloidosis: A proof of concept.

Immunoglobulin light chain (AL) amyloidosis is a fatal complication of B-cell proliferation secondary to deposition of amyloid fibrils in various organs. Urinary exosomes (UEX) are the smallest of the microvesicles excreted in the urine. Previously, we found UEX of patients with AL amyloidosis contained immunoglobulin light chain (LC) oligomers that patients with multiple myeloma did not have. To further explore the role of the LC oligomers, UEX was isolated from an AL amyloidosis patient with progressive renal disease despite achieving a complete response. LC oligomers were identified. Mass spectrometry (MS) of the UEX and serum identified two monoclonal lambda LCs. Proteomics of the trypsin digested amyloid fragments in the kidney by laser microdissection and MS analysis identified a λ6 LC. The cDNA from plasma cell clone was from the IGLV- 6-57 family and it matched the amino acid sequences of the amyloid peptides. The predicted mass of the peptide product of the cDNA matched the mass of one of the two LCs identified in the UEX and serum. UEX combined with MS were able to identify 2 monoclonal lambda LCs that current clinical methods could not. It also identified the amyloidogenic LC which holds potential for response assessment in the future.