C3aR-initiated signaling is a critical mechanism of podocyte injury in membranous nephropathy

The deposition of antipodocyte autoantibodies in the glomerular subepithelial space induces primary membranous nephropathy (MN), the leading cause of nephrotic syndrome worldwide. Taking advantage of the glomerulus-on-a-chip system, we modeled human primary MN induced by anti-PLA2R antibodies. Here we show that exposure of primary human podocytes expressing PLA2R to MN serum results in IgG deposition and complement activation on their surface, leading to loss of the chip permselectivity to albumin. C3a receptor (C3aR) antagonists as well as C3AR gene silencing in podocytes reduced oxidative stress induced by MN serum and prevented albumin leakage. In contrast, inhibition of the formation of the membrane-attack-complex (MAC), previously thought to play a major role in MN pathogenesis, did not affect permselectivity to albumin. In addition, treatment with a C3aR antagonist effectively prevented proteinuria in a mouse model of MN, substantiating the chip findings. In conclusion, using a combination of pathophysiologically relevant in vitro and in vivo models, we established that C3a/C3aR signaling plays a critical role in complement-mediated MN pathogenesis, indicating an alternative therapeutic target for MN.

Albumin determined by bromocresol green leads to erroneous results in routine evaluation of patients with chronic kidney disease

OBJECTIVES

Measurement of plasma albumin is pivotal for clinical decision-making in patients with chronic kidney disease (CKD). Routinely used methods as bromocresol green (BCG) and bromocresol purple (BCP) can suffer from aselectivity, but the impact of aselectivity on the accuracy of plasma albumin results of CKD-patients is still unknown. Therefore, we evaluated the performance of BCG-, BCP- and JCTLM-endorsed immunological methods in patients with various stages of CKD.

METHODS

We evaluated the performance of commonly used albumin methods in patients with CKD stages G1 through G5, the latter divided in two groups based on whether they received hemodialysis treatment. In total, 163 patient plasma samples were measured at 14 laboratories, on six different BCG and BCP-platforms, and four different immunological platforms. The results were compared with an ERM-DA-470k-corrected nephelometric assay. The implications on outcome is evaluated by the proportion of patient results <38 g/L for the diagnosis of protein energy wasting.

RESULTS

Albumin results determined with BCP- and immunological methods showed the best agreement with the target value (92.7 and 86.2 %, respectively vs. 66.7 % for BCG, namely due to overestimation). The relative agreement of each method with the target value was platform-dependent, with larger variability in agreement between platforms noted for BCG and immunological methods (3.2-4.6 and 2.6-5.3 %) as opposed to BCP (0.7-1.5 %). The stage of CKD had similar effects on the variability in agreement for the three method-groups (0.6-1.8 % vs. 0.7-1.5 % vs. 0.4-1.6 %). The differences between methods cause discrepancies in clinical decision-making, as structurally fewer patients were diagnosed with protein energy wasting upon using BCG-based albumin results.

CONCLUSIONS

Our study shows that BCP is fit for the intended use to measure plasma albumin levels in CKD patients from all stages, including patients on hemodialysis. In contrast, most BCG-based platforms falsely overestimate the plasma albumin concentration.

Glomerular diseases in pregnancy: pragmatic recommendations for clinical management

Our understanding of the various aspects of pregnancy in women with kidney diseases has significantly improved in the last decades. Nevertheless, little is known about specific kidney diseases. Glomerular diseases are not only a frequent cause of chronic kidney disease in young women, but combine many challenges in pregnancy: immunologic diseases, hypertension, proteinuria, and kidney tissue damage. An international working group undertook the review of available current literature and elicited expert opinions on glomerular diseases in pregnancy with the aim to provide pragmatic information for nephrologists according to the present state-of-the-art knowledge. This work also highlights areas of clinical uncertainty and emphasizes the need for further collaborative studies to improve maternal and fetal health.

Accuracy of Bioimpedance Spectroscopy in the Detection of Hydration Changes in Patients on Hemodialysis

OBJECTIVES

The body composition monitor (BCM) is a bioimpedance spectroscopy device, specifically developed for patients on hemodialysis (HD) to improve ultrafiltration (UF) programming, based on an objective assessment of the degree of overhydration (OH) at the start of HD. However, its acceptance in clinical practice remains limited because of concerns about the accuracy at the individual level. The aim of this study is to examine the performance of the BCM and to identify means of improvement.

METHODS

Precision of the OH estimate was assessed by 6 consecutive measurements in 24 patients on HD. Accuracy was examined in 45 patients, by comparing the change in OH (ΔOH) during HD with UF volume. Accuracy was considered acceptable if the volume error in individual patients was ≤0.5 L.

RESULTS

The OH estimate had an analytical precision of 1.0 ± 0.4%. The correlation between UF volume and ΔOH was moderate (Slope = 0.66, R² = 0.44, P < .001) and indicated underestimation of UF volume, in particular for high UF volumes. Accuracy at individual level was highly variable. A volume error >0.5 L occurred in 44% of patients. Accuracy improved over the course of HD, with a decrease in total error range from 2.3 L in the first hour to 1.1 L in the final hour of HD.

CONCLUSIONS

The accuracy of BCM volume change estimates is highly variable and below requirements of daily practice. Improvement may be achieved by a switch to an end-of-HD measurement.

IPNA clinical practice recommendations for the diagnosis and management of children with steroid-sensitive nephrotic syndrome

Idiopathic nephrotic syndrome is the most frequent pediatric glomerular disease, affecting from 1.15 to 16.9 per 100,000 children per year globally. It is characterized by massive proteinuria, hypoalbuminemia, and/or concomitant edema. Approximately 85-90% of patients attain complete remission of proteinuria within 4-6 weeks of treatment with glucocorticoids, and therefore, have steroid-sensitive nephrotic syndrome (SSNS). Among those patients who are steroid sensitive, 70-80% will have at least one relapse during follow-up, and up to 50% of these patients will experience frequent relapses or become dependent on glucocorticoids to maintain remission. The dose and duration of steroid treatment to prolong time between relapses remains a subject of much debate, and patients continue to experience a high prevalence of steroid-related morbidity. Various steroid-sparing immunosuppressive drugs have been used in clinical practice; however, there is marked practice variation in the selection of these drugs and timing of their introduction during the course of the disease. Therefore, international evidence-based clinical practice recommendations (CPRs) are needed to guide clinical practice and reduce practice variation. The International Pediatric Nephrology Association (IPNA) convened a team of experts including pediatric nephrologists, an adult nephrologist, and a patient representative to develop comprehensive CPRs on the diagnosis and management of SSNS in children. After performing a systematic literature review on 12 clinically relevant PICO (Patient or Population covered, Intervention, Comparator, Outcome) questions, recommendations were formulated and formally graded at several virtual consensus meetings. New definitions for treatment outcomes to help guide change of therapy and recommendations for important research questions are given.

Novel mouse strains to study circulating permeability factor(s) in primary focal segmental glomerulosclerosis

Recurrence of proteinuria after kidney transplantation in primary focal segmental glomerulosclerosis (FSGS) is unpredictable. Several putative circulating permeability factors (CPFs) have been suggested, but none have been validated. A clinically relevant experimental model is required that demonstrates the presence of CPF(s) in patient material, to study CPF(s) and possibly predict recurrence in patients. We aimed to develop a FSGS-prone Thy-1.1 transgenic mouse model with accelerated proteinuria after injection of samples from patients with FSGS. The Thy-1.1 transgene was backcrossed into 5 mouse strains. The age of onset and severity of spontaneous proteinuria varied between the different genetic backgrounds. 129X1/Sv^Thy-1.1 and 129S2/SvPas^Thy-1.1 mice displayed proteinuria at 4 weeks, whereas Balb/c^Thy-1.1 and C57BL/6J^Thy-1.1 mice developed proteinuria from 6 weeks, and were used further. We determined the maximum protein dose that could be injected without causing protein overload in each background. Balb/c^Thy-1.1 and C57BL/6J^Thy-1.1 males and females were injected with presumably CPF-containing plasmapheresis effluent from 6 FSGS patients, which induced albuminuria particularly in Balb/c^Thy-1.1 males. Unfortunately, no response could be detected when using sera instead of plasmapheresis effluent, serum being more clinically relevant in the context of predicting FSGS recurrence. Considering the differences between responses elicited by serum and plasmapheresis effluent, simultaneously collected serum, plasma, and plasmapheresis effluent were tested. Whereas we could detect responses using a validated in vitro model, none of these presumably CPF-containing samples induced proteinuria in Balb/c^Thy-1.1 males. Thus, we have extensively tested the Thy-1.1 mouse model on different genetic backgrounds with proteinuria after injection of FSGS patient material as clinically relevant readout. The Balb/c^Thy-1.1 male mouse strain demonstrated the most promising results, but to detect CPF activity in FSGS serum e.g. prior to kidney transplantation, this strain clearly lacks sensitivity and is therefore not yet clinically applicable. It could, however, still be used as research tool to study CPFs in patient samples that did induce proteinuria.

Monoclonal gammopathy of renal significance presenting with cryoglobulinemia type I associated severe thrombotic microangiopathy

We report a 53-year-old man who presented with acute renal failure. His medical history revealed a spondyloarthropathy, for which secukinumab was started recently, and a monoclonal gammopathy of unknown significance. Kidney function deteriorated despite the withdrawal of secukinumab and dialysis was started. In the serum, type 1 cryoglobulins were present and a kidney biopsy showed ischaemic glomeruli, with thrombosis of the larger interlobular arteries. Other causes of thrombotic microangiopathy were excluded. Bone marrow immunophenotyping showed 1% monoclonal plasma cells. A diagnosis of monoclonal gammopathy of renal significance was made. Haematological treatment resulted in haematological and renal response.

Selective Binding of Heparin/Heparan Sulfate Oligosaccharides to Factor H and Factor H-Related Proteins: Therapeutic Potential for C3 Glomerulopathies

Complement dysregulation is characteristic of the renal diseases atypical hemolytic uremic syndrome (aHUS) and complement component 3 glomerulopathy (C3G). Complement regulatory protein Factor H (FH) inhibits complement activity, whereas FH-related proteins (FHRs) lack a complement regulatory domain. FH and FHRs compete for binding to host cell glycans, in particular heparan sulfates (HS). HS is a glycosaminoglycan with an immense structural variability, where distinct sulfation patterns mediate specific binding of proteins. Mutations in FH, FHRs, or an altered glomerular HS structure may disturb the FH : FHRs balance on glomerular endothelial cells, thereby leading to complement activation and the subsequent development of aHUS/C3G. In this study, we aimed to identify specific HS structures that could specifically compete off FHRs from HS glycocalyx (HS_Glx), without interfering with FH binding. FH/FHR binding to human conditionally immortalized glomerular endothelial cells (ciGEnCs) and HS_Glx purified from ciGEnC glycocalyx was assessed. HS modifications important for FH/FHR binding to HS_Glx were analyzed using selectively desulfated heparins in competition with purified HS_Glx. We further assessed effects of heparinoids on FHR1- and FHR5-mediated C3b deposition on ciGEnCs. In the presence of C3b, binding of FH, FHR1 and FHR5 to ciGEnCs was significantly increased, whereas binding of FHR2 was minimal. FHR1 and 5 competitively inhibited FH binding to HS_Glx, leading to alternative pathway dysregulation. FHR1 and FHR5 binding was primarily mediated by N-sulfation while FH binding depended on N-, 2-O- and 6-O-sulfation. Addition of 2-O-desulfated heparin significantly reduced FHR1- and FHR5-mediated C3b deposition on ciGEnCs. We identify 2-O-desulfated heparin derivatives as potential therapeutics for C3G and other diseases with dysregulated complement.

The European Rare Kidney Disease Registry (ERKReg): objectives, design and initial results

BACKGROUND

The European Rare Kidney Disease Reference Network (ERKNet) recently established ERKReg, a Web-based registry for all patients with rare kidney diseases. The main objectives of this core registry are to generate epidemiological information, identify current patient cohort for clinical research, explore diagnostic and therapeutic management practices, and monitor treatment performance and patient's outcomes. The registry has a modular design that allows to integrate comprehensive disease-specific registries as extensions to the core database. The diagnosis (Orphacode) and diagnostic information (clinical, imaging, histopathological, biochemical, immunological and genetic) are recorded. Anthropometric, kidney function, and disease-specific management and outcome items informing a set of 61 key performance indicators (KPIs) are obtained annually. Data quality is ensured by automated plausibility checks upon data entry and regular offline database checks prompting queries. Centre KPI statistics and benchmarking are calculated automatically.

RESULTS

Within the first 24 months since its launch, 7607 patients were enrolled to the registry at 45 pediatric and 12 specialized adult nephrology units from 21 countries. A kidney disease diagnosis had been established in 97.1% of these patients at time of enrolment. While 199 individual disease entities were reported by Orphacode, 50% of the cohort could be classified with 11, 80% with 43 and 95% with 92 codes. Two kidney diagnoses were assigned in 6.5% of patients; 5.9% suffered from syndromic disease. Whereas glomerulopathies (54.8%) and ciliopathies including autosomal dominant polycystic kidney disease (ADPKD) (31.5%) were the predominant disease groups among adults, the pediatric disease spectrum encompassed congenital anomalies of the kidney and urinary tract (CAKUT) (33.7%), glomerulopathies (30.7%), ciliopathies (14.0%), tubulopathies (9.2%), thrombotic microangiopathies (5.6%), and metabolic nephropathies (4.1%). Genetically confirmed diagnoses were reported in 24% of all pediatric and 12% adult patients, whereas glomerulopathies had been confirmed by kidney biopsy in 80.4% adult versus 38.5% pediatric glomerulopathy cases.

CONCLUSIONS

ERKReg is a rapidly growing source of epidemiological information and patient cohorts for clinical research, and an innovative tool to monitor management quality and patient outcomes.

Rituximab in Membranous Nephropathy

Membranous nephropathy (MN) is the most common cause of primary nephrotic syndrome among adults. The identification of phospholipase A2 receptor (PLA2R) as target antigen in most patients changed the management of MN dramatically, and provided a rationale for B-cell depleting agents such as rituximab. The efficacy of rituximab in inducing remission has been investigated in several studies, including 3 randomized controlled trials, in which complete and partial remission of proteinuria was achieved in approximately two-thirds of treated patients. Due to its favorable safety profile, rituximab is now considered a first-line treatment option for MN, especially in patients at moderate and high risk of deterioration in kidney function. However, questions remain about how to best use rituximab, including the optimal dosing regimen, a potential need for maintenance therapy, and assessment of long-term safety and efficacy outcomes. In this review, we provide an overview of the current literature and discuss both strengths and limitations of "the new standard."

Impact of diffusion, ultrafiltration, and posture on total body electrical resistance in patients on hemodialysis

Monitoring of hydration in patients on hemodialysis (HD) by currently available bioelectrical impedance analysis (BIA) methods is hampered by limited accuracy. This may be caused by changes in total body electrical resistance (TBER) that are induced by processes other than ultrafiltration (UF). To identify these sources of error, we examined the impact of UF, diffusion, and postural change (PC), separately. Extracellular TBER (TBER_e) was measured by bioimpedance spectroscopy every 30 min in 23 patients on HD, for 2 h during diffusion-only (DO), followed by 2-h UF-only (UFO). The impact of PC from upright to semi-recumbent position was assessed by a 2-h TBER_e measurement on the day after HD. TBER_e increased by 23.5 ± 12.4 Ω (P < 0.001) during DO and by 40.0 ± 16.2 Ω (P < 0.001) during UFO. PC, evaluated on a separate day, was associated with an increase in TBER_e of 27.6 ± 26.0 Ω (P < 0.001). TBER_e changes during DO were mainly attributed to PC and to a lesser extent to electrolyte exchange. Extrapolation of the data to a conventional 4-h HD session indicates that about 32% of the total increase in TBER_e is not related to UF. In conclusion, a significant part of the increase in TBER during HD is not related to UF but can be attributed to other processes such as the effects of PC and diffusion-related electrolyte exchange. These factors have to be taken into account when TBER-guided UF is considered.NEW & NOTEWORTHY Current BIA methods have limited accuracy in patients on HD. This may be related to the incorrect assumption that all changes in total body electrical resistance (TBER) are caused by changes in body water volumes. The present study indicates that two-thirds of the change in TBER during a conventional 4-h HD session can be attributed to fluid extraction, and that the remaining part is caused by other processes such as postural change and electrolyte exchange. This may cause volume prediction errors when not recognized.

The STARMEN trial indicates that alternating treatment with corticosteroids and cyclophosphamide is superior to sequential treatment with tacrolimus and rituximab in primary membranous nephropathy

A cyclical corticosteroid-cyclophosphamide regimen is recommended for patients with primary membranous nephropathy at high risk of progression. We hypothesized that sequential therapy with tacrolimus and rituximab is superior to cyclical alternating treatment with corticosteroids and cyclophosphamide in inducing persistent remission in these patients. This was tested in a randomized, open-label controlled trial of 86 patients with primary membranous nephropathy and persistent nephrotic syndrome after six-months observation and assigned 43 each to receive six-month cyclical treatment with corticosteroid and cyclophosphamide or sequential treatment with tacrolimus (full-dose for six months and tapering for another three months) and rituximab (one gram at month six). The primary outcome was complete or partial remission of nephrotic syndrome at 24 months. This composite outcome occurred in 36 patients (83.7%) in the corticosteroid-cyclophosphamide group and in 25 patients (58.1%) in the tacrolimus-rituximab group (relative risk 1.44; 95% confidence interval 1.08 to 1.92). Complete remission at 24 months occurred in 26 patients (60%) in the corticosteroid-cyclophosphamide group and in 11 patients (26%) in the tacrolimus-rituximab group (2.36; 1.34 to 4.16). Anti-PLA2R titers showed a significant decrease in both groups but the proportion of anti-PLA2R-positive patients who achieved immunological response (depletion of anti-PLA2R antibodies) was significantly higher at three and six months in the corticosteroid-cyclophosphamide group (77% and 92%, respectively), as compared to the tacrolimus-rituximab group (45% and 70%, respectively). Relapses occurred in one patient in the corticosteroid-cyclophosphamide group, and three patients in the tacrolimus-rituximab group. Serious adverse events were similar in both groups. Thus, treatment with corticosteroid-cyclophosphamide induced remission in a significantly greater number of patients with primary membranous nephropathy than tacrolimus-rituximab.

Conversion of Urine Protein-Creatinine Ratio or Urine Dipstick Protein to Urine Albumin-Creatinine Ratio for Use in Chronic Kidney Disease Screening and Prognosis : An Individual Participant-Based Meta-analysis

BACKGROUND

Although measuring albuminuria is the preferred method for defining and staging chronic kidney disease (CKD), total urine protein or dipstick protein is often measured instead.

OBJECTIVE

To develop equations for converting urine protein-creatinine ratio (PCR) and dipstick protein to urine albumin-creatinine ratio (ACR) and to test their diagnostic accuracy in CKD screening and staging.

DESIGN

Individual participant-based meta-analysis.

SETTING

12 research and 21 clinical cohorts.

PARTICIPANTS

919 383 adults with same-day measures of ACR and PCR or dipstick protein.

MEASUREMENTS

Equations to convert urine PCR and dipstick protein to ACR were developed and tested for purposes of CKD screening (ACR ≥30 mg/g) and staging (stage A2: ACR of 30 to 299 mg/g; stage A3: ACR ≥300 mg/g).

RESULTS

Median ACR was 14 mg/g (25th to 75th percentile of cohorts, 5 to 25 mg/g). The association between PCR and ACR was inconsistent for PCR values less than 50 mg/g. For higher PCR values, the PCR conversion equations demonstrated moderate sensitivity (91%, 75%, and 87%) and specificity (87%, 89%, and 98%) for screening (ACR >30 mg/g) and classification into stages A2 and A3, respectively. Urine dipstick categories of trace or greater, trace to +, and ++ for screening for ACR values greater than 30 mg/g and classification into stages A2 and A3, respectively, had moderate sensitivity (62%, 36%, and 78%) and high specificity (88%, 88%, and 98%). For individual risk prediction, the estimated 2-year 4-variable kidney failure risk equation using predicted ACR from PCR had discrimination similar to that of using observed ACR.

LIMITATION

Diverse methods of ACR and PCR quantification were used; measurements were not always performed in the same urine sample.

CONCLUSION

Urine ACR is the preferred measure of albuminuria; however, if ACR is not available, predicted ACR from PCR or urine dipstick protein may help in CKD screening, staging, and prognosis.

PRIMARY FUNDING SOURCE

National Institute of Diabetes and Digestive and Kidney Diseases and National Kidney Foundation.

Rituximab in adult minimal change disease and focal segmental glomerulosclerosis - What is known and what is still unknown?

Primary forms of minimal change disease and focal segmental glomerulosclerosis are rare podocytopathies and clinically characterized by nephrotic syndrome. Glucocorticoids are the cornerstone of the initial immunosuppressive treatment in these two entities. Especially among adults with minimal change disease or focal segmental glomerulosclerosis, relapses, steroid dependence or resistance are common and necessitate re-initiation of steroids and other immunosuppressants. Effective steroid-sparing therapies and introduction of less toxic immunosuppressive agents are urgently needed to reduce undesirable side effects, in particular for patients whose disease course is complex. Rituximab, a B cell depleting monoclonal antibody, is increasingly used off-label in these circumstances, despite a low level of evidence for adult patients. Hence, critical questions concerning drug-safety, long-term efficacy and the optimal regimen for rituximab-treatment remain unanswered. Evidence in the form of large, multicenter studies and randomized controlled trials are urgently needed to overcome these limitations.

Glomerular Outgrowth as an Ex Vivo Assay to Analyze Pathways Involved in Parietal Epithelial Cell Activation

Parietal epithelial cell (PEC) activation is one of the key factors involved in the development and progression of glomerulosclerosis. Inhibition of pathways involved in parietal epithelial cell activation could therefore be a tool to attenuate the progression of glomerular diseases. This article describes a method to culture and analyze parietal epithelial cell outgrowth of encapsulated glomeruli isolated from mouse kidney. After dissecting isolated mouse kidneys, the tissue is minced, and glomeruli are isolated by sieving. Encapsulated glomeruli are collected, and single glomeruli are cultured for 6 days to obtain glomerular outgrowth of parietal epithelial cells. During this period, parietal epithelial cell proliferation and migration can be analyzed by determining the cell number or the surface area of outgrowing cells. This assay can therefore be used as a tool to study the effects of an altered gene expression in transgenic- or knockout-mice or the effects of culture conditions on parietal epithelial cell growth characteristics and signaling. Using this method, important pathways involved in the process of parietal epithelial cell activation and consequently in glomerulosclerosis can be studied.

Neuropeptide Y and chronic kidney disease progression: a cohort study

Background

Neuropeptide Y (NPY) is a sympathetic neurotransmitter that has been implicated in various disorders including obesity, gastrointestinal and cardiovascular diseases.

Methods

We investigated the relationship between circulating NPY and the progression of the glomerular filtration rate (GFR) and proteinuria and the risk for a combined renal endpoint (>30% GFR loss, dialysis/transplantation) in two European chronic kidney disease (CKD) cohorts including follow-up of 753 and 576 patients for 36 and 57 months, respectively.

Results

Average plasma NPY was 104 ± 32 pmol/L in the first CKD cohort and 119 ± 41 pmol/L in the second one. In separate analyses of the two cohorts, NPY associated with the progression of the estimated GFR (eGFR) and proteinuria over time in both unadjusted and adjusted {eGFR: -3.60 mL/min/1.73 m2 [95% confidence interval (CI): -4.46 to - 2.74] P < 0.001 and -0.83 mL/min/1.73 m2 (-1.41 to - 0.25, P = 0.005); proteinuria: 0.18 g/24 h (0.11-0.25) P < 0.001 and 0.07 g/24 h (0.005-0.14) P = 0.033} analyses by the mixed linear model. Accordingly, in a combined analysis of the two cohorts accounting for the competitive risk of death (Fine and Gray model), NPY predicted (P = 0.005) the renal endpoint [sub-distribution hazard ratio (SHR): 1.09; 95% CI: 1.03-1.16; P = 0.005] and the SHR in the first cohort (1.14, 95% CI: 1.04-1.25) did not differ (P = 0.25) from that in the second cohort (1.06, 95% CI: 0.98-1.15).

Conclusions

NPY associates with proteinuria and faster CKD progression as well as with a higher risk of kidney failure. These findings suggest that the sympathetic system and/or properties intrinsic to the NPY molecule may play a role in CKD progression.

Genetic Identification of Two Novel Loci Associated with Steroid-Sensitive Nephrotic Syndrome

BACKGROUND

Steroid-sensitive nephrotic syndrome (SSNS), the most common form of nephrotic syndrome in childhood, is considered an autoimmune disease with an established classic HLA association. However, the precise etiology of the disease is unclear. In other autoimmune diseases, the identification of loci outside the classic HLA region by genome-wide association studies (GWAS) has provided critical insights into disease pathogenesis. Previously conducted GWAS of SSNS have not identified non-HLA loci achieving genome-wide significance.

METHODS

In an attempt to identify additional loci associated with SSNS, we conducted a GWAS of a large cohort of European ancestry comprising 422 ethnically homogeneous pediatric patients and 5642 ethnically matched controls.

RESULTS

The GWAS found three loci that achieved genome-wide significance, which explain approximately 14% of the genetic risk for SSNS. It confirmed the previously reported association with the HLA-DR/DQ region (lead single-nucleotide polymorphism [SNP] rs9273542, P=1.59×10^-43; odds ratio [OR], 3.39; 95% confidence interval [95% CI], 2.86 to 4.03) and identified two additional loci outside the HLA region on chromosomes 4q13.3 and 6q22.1. The latter contains the calcium homeostasis modulator family member 6 gene CALHM6 (previously called FAM26F). CALHM6 is implicated in immune response modulation; the lead SNP (rs2637678, P=1.27×10^-17; OR, 0.51; 95% CI, 0.44 to 0.60) exhibits strong expression quantitative trait loci effects, the risk allele being associated with lower lymphocytic expression of CALHM6.

CONCLUSIONS

Because CALHM6 is implicated in regulating the immune response to infection, this may provide an explanation for the typical triggering of SSNS onset by infections. Our results suggest that a genetically conferred risk of immune dysregulation may be a key component in the pathogenesis of SSNS.

Predicting kidney failure from longitudinal kidney function trajectory: A comparison of models

Rationale & objective

Early prediction of chronic kidney disease (CKD) progression to end-stage kidney disease (ESKD) currently use Cox models including baseline estimated glomerular filtration rate (eGFR) only. Alternative approaches include a Cox model that includes eGFR slope determined over a baseline period of time, a Cox model with time varying GFR, or a joint modeling approach. We studied if these more complex approaches may further improve ESKD prediction.

Study design

Prospective cohort.

Setting & participants

We re-used data from two CKD cohorts including patients with baseline eGFR >30ml/min per 1.73m². MASTERPLAN (N = 505; 55 ESKD events) was used as development dataset, and NephroTest (N = 1385; 72 events) for validation.

Predictors

All models included age, sex, eGFR, and albuminuria, known prognostic markers for ESKD.

Analytical approach

We trained the models on the MASTERPLAN data and determined discrimination and calibration for each model at 2 years follow-up for a prediction horizon of 2 years in the NephroTest cohort. We benchmarked the predictive performance against the Kidney Failure Risk Equation (KFRE).

Results

The C-statistics for the KFRE was 0.94 (95%CI 0.86 to 1.01). Performance was similar for the Cox model with time-varying eGFR (0.92 [0.84 to 0.97]), eGFR (0.95 [0.90 to 1.00]), and the joint model 0.91 [0.87 to 0.96]). The Cox model with eGFR slope showed the best calibration.

Conclusion

In the present studies, where the outcome was rare and follow-up data was highly complete, the joint models did not offer improvement in predictive performance over more traditional approaches such as a survival model with time-varying eGFR, or a model with eGFR slope.

Development and Pretesting of a Questionnaire to Assess Patient Experiences and Satisfaction with Medications (PESaM Questionnaire)

Background

The aim of this study was to develop, together with the Lung Foundation Netherlands and Dutch Kidney Patients Association, patients and clinicians, a measure to evaluate patient experiences with the orphan drugs pirfenidone (for idiopathic pulmonary fibrosis [IPF]) and eculizumab (for atypical haemolytic uraemic syndrome [aHUS]), as well as a generic measure of patient experiences and satisfaction with medications.

Methods

Development of the Patient Experiences and Satisfaction with Medications (PESaM) questionnaire consisted of four phases: literature review (phase I); focus groups and individual patient interviews (phase II); item generation (phase III); and face and content validity testing (phase IV). Literature review aimed to identify existing disease-specific and generic patient experience measures to provide guidance on the domains of medication use relevant to patients, the number of items and type of response categories, and to generate an initial pool of items. Subsequent focus groups and patient interviews were conducted to gain insight into the perceived effectiveness of the therapies, the burden of side effects, and how the medication impacted on a patient’s daily life. Focus groups and interviews were recorded and transcribed verbatim. Coding was carried out by highlighting passages in the text and assigning each passage a code representing the following predefined categories: (1) perceived effectiveness; (2) side effects; (3) ease of use; and (4) impact of medication. Using data from phase I and II, a panel of experts selected items relevant for inclusion in the questionnaire. Individual patient interviews with IPF and aHUS patients (n = 18), using a retrospective verbal probing technique, were conducted to assess face validity, time needed to fill out the questionnaire, and content validity.

Results

The PESaM questionnaire that was developed consisted of two disease-specific modules that assessed patient experiences with pirfenidone for the treatment of IPF, and eculizumab for the treatment of aHUS, a generic module, applicable to any medication, and a module to assess patient expectations. Review of the literature identified multiple disease- or medication-specific questionnaires and two generic patient satisfaction questionnaires. Common domains across most questionnaires were effectiveness, side effects, ease of use and overall satisfaction. Patient interviews revealed the social impact (e.g. unable to go outside) of side effects such as photosensitivity associated with pirfenidone and the risk of infection associated with eculizumab. Each PESaM module focuses on patients’ perceived effectiveness of the medication, side effects, and ease of use, and the impact these aspects have on physical and emotional health and daily life. The generic module additionally includes items related to satisfaction with the medication. Individual interviews with patients in phase IV confirmed, in general, that questions and response options of the modules were clear and content validity was good. The mean time to complete the modules ranged from 6 min for the disease-specific (aHUS) module to 9 min for the generic module.

Conclusions

We developed the PESaM questionnaire to quantitatively assess patient experiences and satisfaction with medications. A validation study is currently underway to examine the psychometric properties of the PESaM questionnaire.

Electronic supplementary material

The online version of this article (doi:10.1007/s40271-017-0234-z) contains supplementary material, which is available to authorized users.

Differential diagnosis of thrombotic microangiopathy in nephrology

Background

The differential diagnosis of thrombotic microangiopathy (TMA) is complex however the rapid diagnosis of the underlying condition is vital to inform urgent treatment decisions. A survey was devised with the objective of understanding current practices across Europe and the Middle East, and of challenges when diagnosing the cause of TMA.

Methods

Over 450 clinicians, from 16 countries were invited to complete an online survey.

Results

Of 254 respondents, the majority were nephrologists, had >10 years’ experience in their specialty, and had diagnosed a patient with TMA. The triad of thrombocytopenia, haemolytic anaemia and acute kidney injury are the main diagnostic criteria used. Responses indicate that a differential diagnosis of TMA is usually made within 1–2 (53%) or 3–4 days (26%) of presentation. Similarly, therapy is usually initiated within the first 4 days (74%), however 13% report treatment initiation >1-week post-presentation. Extrarenal symptoms and a panoply of other conditions are considered when assessing the differential diagnosis of TMA. While 70 and 78% of respondents stated they always request complement protein levels and ADAMTS13 activity, respectively. Diagnostic considerations of paediatric and adult nephrologists varied. A greater proportion of paediatric than adult nephrologists consider extrarenal manifestations clinically related to a diagnosis of TMA; pulmonary (45% vs. 18%), gastrointestinal (67% vs. 50%), CNS (96% vs. 84%) and cardiovascular (54% vs. 42%), respectively. Variability in the availability of guidelines and extent of family history taken was also evident.

Conclusions

This survey reveals the variability of current practices and the need for increased urgency among physicians in the differential diagnosis of TMA, despite their experience. Above all, the survey highlights the need for international clinical guidelines to provide systematically developed recommendations for understanding the relevance of complement protein levels, complement abnormalities and ADAMTS13 testing, in making a differential diagnosis of TMA. Such clinical guidelines would enable physicians to make a more rapid and informed diagnosis of TMA, therefore initiate effective treatment earlier, with a consequent improvement in patient outcomes.

Electronic supplementary material

The online version of this article (doi: 10.1186/s12882-017-0727-y) contains supplementary material, which is available to authorized users.

Clinical Relevance of Differences in Glomerular Filtration Rate Estimations in Frail Older People by Creatinine- vs. Cystatin C-Based Formulae

BACKGROUND

The risk of incorrect medication dosing is high in frail older people. Therefore, accurate assessment of the glomerular filtration rate is important.

OBJECTIVE

The objective of this study was to compare the estimated glomerular filtration rate using creatinine- and cystatin C-based formulae, the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations, in frail older people. We hypothesized that frailty determines the difference between the creatinine- and cystatin C-based formulae.

METHODS

The mean difference between CKD-EPI creatinine and cystatin C was determined using (cross-sectional) data of 55 patients (mean age 73 years) admitted to a psychiatric ward for older adults. The level of agreement of these estimations was assessed by a Bland-Altman analysis. In all patients, the Rockwood's Frailty Index was derived and correlated with the mean difference between CKD-EPI creatinine and cystatin C.

RESULTS

The mean difference between CKD-EPI creatinine (mean 71.2 mL/min/1.73 m²) and CKD-EPI cystatin C (mean 57.6 mL/min/1.73 m²) was 13.6 mL/min/1.73 m² (p < 0.0001). The two standard deviation limit in the Bland-Altman plot was large (43.2 mL/min/1.73 m²), which represents a low level of agreement. The Frailty Index did not correlate with the mean difference between the creatinine- and cystatin C-based glomerular filtration rate (Pearson correlation coefficient 0.182, p = 0.184).

CONCLUSIONS

There was a significant gap between a creatinine- and cystatin C-based estimation of glomerular filtration rate, irrespective of frailty. The range of differences between the commonly used estimated glomerular filtration rate formulae might result in clinically relevant differences in drug prescription and differences in chronic kidney disease staging.

Risk factors for progression in children and young adults with IgA nephropathy: an analysis of 261 cases from the VALIGA European cohort

BACKGROUND

There is a need for early identification of children with immunoglobulin A nephropathy (IgAN) at risk of progression of kidney disease.

METHODS

Data on 261 young patients [age <23 years; mean follow-up of 4.9 (range 2.5-8.1) years] enrolled in VALIGA, a study designed to validate the Oxford Classification of IgAN, were assessed. Renal biopsies were scored for the presence of mesangial hypercellularity (M1), endocapillary hypercellularity (E1), segmental glomerulosclerosis (S1), tubular atrophy/interstitial fibrosis (T1-2) (MEST score) and crescents (C1). Progression was assessed as end stage renal disease and/or a 50 % loss of estimated glomerular filtration rate (eGFR) (combined endpoint) as well as the rate of renal function decline (slope of eGFR). Cox regression and tree classification binary models were used and compared.

RESULTS

In this cohort of 261 subjects aged <23 years, Cox analysis validated the MEST M, S and T scores for predicting survival to the combined endpoint but failed to prove that these scores had predictive value in the sub-group of 174 children aged <18 years. The regression tree classification indicated that patients with M1 were at risk of developing higher time-averaged proteinuria (p < 0.0001) and the combined endpoint (p < 0.001). An initial proteinuria of ≥0.4 g/day/1.73 m² and an eGFR of <90 ml/min/1.73 m² were determined to be risk factors in subjects with M0. Children aged <16 years with M0 and well-preserved eGFR (>90 ml/min/1.73 m²) at presentation had a significantly high probability of proteinuria remission during follow-up and a higher remission rate following treatment with corticosteroid and/or immunosuppressive therapy.

CONCLUSION

This new statistical approach has identified clinical and histological risk factors associated with outcome in children and young adults with IgAN.

A European multicentre and open-label controlled randomized trial to evaluate the efficacy of Sequential treatment with TAcrolimus-Rituximab versus steroids plus cyclophosphamide in patients with primary MEmbranous Nephropathy: the STARMEN study

BACKGROUND

Patients with primary membranous nephropathy (MN) and persistent nephrotic syndrome have a high risk of progression to end-stage renal disease. The Ponticelli protocol (steroids with alkylating agents) is the most effective immunosuppressive therapy for this condition, but it has severe adverse effects. Tacrolimus and rituximab have demonstrated efficacy for remission of nephrotic syndrome in MN with a safer profile. However, the published evidence is largely based on small or short-term observational studies, historical cohorts, comparisons with conservative therapy or clinical trials without appropriate control groups, and there is no head-to-head comparison with the Ponticelli protocol.

METHODS

The STARMEN randomized clinical trial will compare the efficacy of sequential tacrolimus-rituximab therapy with a modified Ponticelli protocol (steroids plus cyclophosphamide). The trial will also evaluate the role of antibodies against the M-type phospholipase A2 receptor (anti-PLA2R) and other antibodies as markers of response to treatment and long-term prognosis.

RESULTS

The trial has already started with 23 patients having been enrolled as of 1 April 2015, an estimated 21.7% of the estimated sample.

Detection of activated parietal epithelial cells on the glomerular tuft distinguishes early focal segmental glomerulosclerosis from minimal change disease

In rodents, parietal epithelial cells (PECs) migrating onto the glomerular tuft participate in the formation of focal segmental glomerulosclerosis (FSGS) lesions. We investigated whether immunohistologic detection of PEC markers in the initial biopsies of human patients with first manifestation of idiopathic nephrotic syndrome with no immune complexes can improve the sensitivity to detect sclerotic lesions compared with standard methods. Ninety-five renal biopsies were stained for claudin-1 (PEC marker), CD44 (activated PECs), and LKIV69 (PEC matrix); 38 had been diagnosed as early primary FSGS and 57 as minimal change disease. PEC markers were detected on the tuft in 87% of the biopsies of patients diagnosed as primary FSGS. PEC markers were detected in FSGS lesions from the earliest stages of disease. In minimal change disease, no PEC activation was observed by immunohistology. However, in 25% of biopsies originally diagnosed as minimal change disease the presence of small lesions indicative of a sclerosing process were detected, which were undetectable on standard periodic acid-Schiff staining, even though only a single histologic section for each PEC marker was evaluated. Staining for LKIV69 detected lesions with the highest sensitivity. Two novel PEC markers A-kinase anchor protein 12 and annexin A3 exhibited similar sensitivity. In summary, detection of PECs on the glomerular tuft by immunostaining improves the differentiation between minimal change disease and primary FSGS and may serve to guide clinical decision making.

Subtotal ablation of parietal epithelial cells induces crescent formation

Parietal epithelial cells (PECs) of the renal glomerulus contribute to the formation of both cellular crescents in rapidly progressive GN and sclerotic lesions in FSGS. Subtotal transgenic ablation of podocytes induces FSGS but the effect of specific ablation of PECs is unknown. Here, we established an inducible transgenic mouse to allow subtotal ablation of PECs. Proteinuria developed during doxycycline-induced cellular ablation but fully reversed 26 days after termination of doxycycline administration. The ablation of PECs was focal, with only 30% of glomeruli exhibiting histologic changes; however, the number of PECs was reduced up to 90% within affected glomeruli. Ultrastructural analysis revealed disruption of PEC plasma membranes with cytoplasm shedding into Bowman's space. Podocytes showed focal foot process effacement, which was the most likely cause for transient proteinuria. After >9 days of cellular ablation, the remaining PECs formed cellular extensions to cover the denuded Bowman's capsule and expressed the activation marker CD44 de novo. The induced proliferation of PECs persisted throughout the observation period, resulting in the formation of typical cellular crescents with periglomerular infiltrate, albeit without accompanying proteinuria. In summary, subtotal ablation of PECs leads the remaining PECs to react with cellular activation and proliferation, which ultimately forms cellular crescents.

Renal progenitor cells contribute to hyperplastic lesions of podocytopathies and crescentic glomerulonephritis

Glomerular injury can involve excessive proliferation of glomerular epithelial cells, resulting in crescent formation and obliteration of Bowman's space. The origin of these hyperplastic epithelial cells in different glomerular disorders is controversial. Renal progenitors localized to the inner surface of Bowman's capsule can regenerate podocytes, but whether dysregulated proliferation of these progenitors contributes to crescent formation is unknown. In this study, we used confocal microscopy, laser capture microdissection, and real-time quantitative reverse transcriptase-PCR to demonstrate that hypercellular lesions of different podocytopathies and crescentic glomerulonephritis consist of three distinct populations: CD133(+)CD24(+)podocalyxin (PDX)(-)nestin(-) renal progenitors, CD133(+)CD24(+)PDX(+)nestin(+) transitional cells, and CD133(-)CD24(-)PDX(+)nestin(+) differentiated podocytes. In addition, TGF-beta induced CD133(+)CD24(+) progenitors to produce extracellular matrix, and these were the only cells to express the proliferation marker Ki67. Taken together, these results suggest that glomerular hyperplastic lesions derive from the proliferation of renal progenitors at different stages of their differentiation toward mature podocytes, providing an explanation for the pathogenesis of hyperplastic lesions in podocytopathies and crescentic glomerulonephritis.

Progressive renal disease despite immunosuppressive therapy in a patient with Wegener s granulomatosis

We present a patient with Morbus Wegener and crescentic glomerulonephritis. Treatment with cyclophosphamide and prednisolone resulted in the disappearance of signs and symptoms of systemic inflammation. However, renal function deteriorated. Renal biopsy showed evidence of continuing capillary necrosis. Renal function improved with added plasmapheresis treatment. This case report illustrates that in patients with vasculitis necrotizing glomerulonephritis may remain active despite immunosuppressive therapy, even in the absence of extrarenal disease activity.