Long-term prognosis of clinically early IgA nephropathy is not always favorable

An enhanced machine learning approach for effective prediction of IgA nephropathy patients with severe proteinuria based on clinical data

IgA Nephropathy (IgAN) is a disease of the glomeruli that may eventually lead to chronic kidney disease or kidney failure. The signs and symptoms of IgAN nephropathy are usually not specific enough and are similar to those of other glomerular or inflammatory diseases. This makes a correct diagnosis more difficult. This study collected data from a sample of adult patients diagnosed with primary IgAN at the First Affiliated Hospital of Wenzhou Medical University, with proteinuria ≥1 g/d at the time of diagnosis. Based on these samples, we propose a machine learning framework based on weIghted meaN oF vectOrs (INFO). An enhanced COINFO algorithm is proposed by merging INFO, Cauchy Mutation (CM) and Oppositional-based Learning (OBL) strategies. At the same time, COINFO and Support Vector Machine (SVM) were integrated to construct the BCOINFO-SVM framework for IgAN diagnosis and prediction. Initially, the proposed enhanced COINFO is evaluated using the IEEE CEC2017 benchmark problems, with the outcomes demonstrating its efficient optimization capability and accuracy in convergence. Furthermore, the feature selection capability of the proposed method is verified on the public medical datasets. Finally, the auxiliary diagnostic experiment was carried out through IgAN real sample data. The results demonstrate that the proposed BCOINFO-SVM can screen out essential features such as High-Density Lipoprotein (HDL), Uric Acid (UA), Cardiovascular Disease (CVD), Hypertension and Diabetes. Simultaneously, the BCOINFO-SVM model achieves an accuracy of 98.56%, with sensitivity at 96.08% and specificity at 97.73%, making it a potential auxiliary diagnostic model for IgAN.

The Treatment of Primary IgA Nephropathy: Change, Change, Change

IgA nephropathy (IgAN) is the most common glomerular disease in the world. However, the approach to treatment remains controversial. There has been an explosion of clinical trials over the past decade both to further examine corticosteroid use and usher in additional treatment considerations, including 2 newly approved therapies for IgAN. Sodium glucose cotransporter 2 inhibitors are proving to be effective therapy across proteinuric chronic kidney diseases, and IgAN is not likely to be an exception. Further supportive agents are looking highly promising and so are novel agents that specifically focus on the pathophysiology of this disease, including endothelin blockade, complement inhibition, and B-cell targeted strategies. We suggest a present-day approach to treatment of individuals with IgAN, expose the limitations in our knowledge, and discuss new treatments that may arise, hoping they come with evidence about optimal utilization. Change appears to be inevitable for our approach to the treatment of IgA nephropathy. This is truly an exciting and optimistic time.

Validation of the international IgA nephropathy prediction tool in a French cohort beyond 10 years after diagnosis

INTRODUCTION

The International IgA Nephropathy Network developed a tool (IINN-PT) for predicting the risk of end-stage renal disease (ESRD) or a 50% decline in the estimated glomerular filtration rate (eGFR). We aimed to validate this tool in a French cohort with longer follow-up than previously published validation studies.

METHODS

The predicted survival of patients with biopsy-proven immunoglobulin A nephropathy (IgAN) from the Saint Etienne University Hospital cohort was computed with IINN-PT models with or without ethnicity. The primary outcome was the occurrence of either ESRD or a 50% decline in eGFR. The models' performances were evaluated through c-statistics, discrimination and calibration analysis.

RESULTS

There were 473 patients with biopsy-proven IgAN, with a median follow-up of 12.4 years. Models with and without ethnicity showed areas under the curve (95% confidence interval) of 0.817 (0.765; 0.869) and 0.833 (0.791; 0.875) and R2D of 0.28 and 0.29, respectively, and an excellent discrimination of groups of increasing predicted risk (P < .001). The calibration analysis was good for both models up to 15 years after diagnosis. The model without ethnicity exhibited a mathematical issue of survival function after 15 years.

DISCUSSION

The IINN-PT provided good performances even after 10 years post-biopsy as showed by our study based on a cohort with a longer follow-up than previous cohorts (12.4 versus <6 years). The model without ethnicity exhibited better performances up to 15 years but became aberrant beyond this point due to a mathematical issue affecting the survival function. Our study sheds light on the usefulness of integrating ethnicity as a covariable for prediction of IgAN course.

Prognostic factors of IgA nephropathy presenting with mild proteinuria at the time of diagnosis (a multicenter cohort study)

BACKGROUND

Clinical factors affecting renal prognosis in patients with immunoglobulin A nephropathy (IgAN) and low urinary protein excretion (U-Prot) remain unclear. This study evaluated such factors in patients with clinical grade I (CG-I) IgAN with U-Prot < 0.5 g/day.

METHODS

This secondary analysis of a previous retrospective study included 394 patients with CG-I IgAN. The primary outcome was the first occurrence of a 1.5-fold increase in serum creatinine levels from baseline. Factors related to renal prognosis were examined using univariate and multivariate Cox regression analyses. CG-I was divided into C-Grade Ia (CG-Ia) (n = 330) with baseline eGFR ≥ 60 ml/min/1.73 m², and C-Grade Ib (CG-Ib) (n = 64) with baseline eGFR < 60 ml/min/1.73 m². Outcome incidence was compared between conservative and aggressive therapy (corticosteroids and/or tonsillectomy) groups.

RESULTS

Overall outcome incidence was significantly higher in CG-Ib than in CG-Ia; the cumulative incidence was significantly higher in CG-Ib (hazard ratio, 9.67; 95% confidence interval, 2.90-32.23). Older age, higher IgA levels, eGFR < 60 mL/min/1.73 m², lower eGFR at baseline were independent prognostic factors for CG-I. Older age, lower eGFR, higher IgA levels at baseline, and U-Prot remission at 1-year post-diagnosis were independent prognostic factors for CG-Ib. Aggressive therapy tended to suppress the cumulative outcome incidence compared with conservative therapy in CG-Ib (p = 0.087).

CONCLUSION

An eGFR < 60 mL/min/1.73 m² is a significant predictor of renal prognosis in patients with IgAN and U-Prot < 0.5 g/day.

Causal effects between gut microbiota and IgA nephropathy: a bidirectional Mendelian randomization study

Background

Therapeutic approaches that target the gut microbiota (GM) may be helpful in the potential prevention and treatment of IgA nephropathy (IgAN). Meanwhile, relevant studies demonstrated a correlation between GM and IgAN, however, these confounding evidence cannot prove a causal relationship between GM and IgAN.

Methods

Based on the data from the GM genome-wide association study (GWAS) of MiBioGen and the IgAN GWAS data from the FinnGen research. A bi-directional Mendelian randomization (MR) study was performed to explore the causal relationship between GM and IgAN. We used inverse variance weighted (IVW) method as the primary method to determine the causal relationship between exposure and outcome in our MR study. Besides, we used additional analysis (MR-Egger, weighted median) and sensitivity analysis (Cochrane's Q test, MR-Egger and MR-PRESSO) to select significant results, followed by Bayesian model averaging (MR-BMA) to test the results of MR study. Finally, a reverse MR analysis was conducted to estimate the probability of reverse causality.

Results

At the locus-wide significance level, the results of IVW method and additional analysis showed that Genus Enterorhabdus was a protective factor for IgAN [OR: 0.456, 95% CI: 0.238-0.875, p=0.023], while Genus butyricicoccus was a risk factor for IgAN [OR: 3.471, 95% CI: 1.671-7.209, p=0.0008]. In the sensitivity analysis, no significant pleiotropy or heterogeneity of the results was found.

Conclusion

Our study revealed the causal relationship between GM and IgAN, and expanded the variety of bacterial taxa causally related to IgAN. These bacterial taxa could become novel biomarkers to facilitate the development of targeted therapies for IgAN, developing our understanding of the "gut-kidney axis".

Galactose-Deficient IgA1 as a Candidate Urinary Marker of IgA Nephropathy

In patients with IgA nephropathy (IgAN), circulatory IgA1 and IgA1 in the mesangial deposits contain galactose-deficient IgA1 (Gd-IgA1). Some of the Gd-IgA1 from the glomerular deposits is excreted in the urine and thus urinary Gd-IgA1 may represent a disease-specific marker. We recruited 338 Japanese biopsy-proven IgAN patients and 120 patients with other renal diseases (disease controls). Urine samples collected at the time of renal biopsy were used to measure Gd-IgA1 levels using a specific monoclonal antibody (KM55 mAb). Urinary Gd-IgA1 levels were significantly higher in patients with IgAN than in disease controls. Moreover, urinary Gd-IgA1 was significantly correlated with the severity of the histopathological parameters in IgAN patients. Next, we validated the use of urinary Gd-IgA1 levels in the other Asian cohorts. In the Korean cohort, urinary Gd-IgA1 levels were also higher in patients with IgAN than in disease controls. Even in Japanese patients with IgAN and trace proteinuria (less than 0.3 g/gCr), urinary Gd-IgA1 was detected. Thus, urinary Gd-IgA1 may be an early disease-specific biomarker useful for determining the disease activity of IgAN.

Expression of CCL2, FOS, and JUN May Help to Distinguish Patients With IgA Nephropathy From Healthy Controls

Background

IgA nephropathy (IgAN), the most common type of glomerulonephritis worldwide, can only be diagnosed mainly by renal biopsy owing to lack of effective biomarkers. It is urgent to explore and identify the potential diagnostic biomarkers through assessing the gene expression profiles of patients with IgAN.

Methods

Two datasets were obtained from the Gene Expression Omnibus (GEO) database, including GSE115857 (55 IgAN, 7 living healthy donors) and GSE35487 (25 IgAN, 6 living healthy donors), then underwent differentially expressed genes (DEGs) and function enrichment analyses utilizing R packages. The common gene list was screened out between DEGs and immune-associated genes by Venn diagram, then performed gene-gene interaction, protein-protein interaction (PPI) and function enrichment analyses. Top three immune-associated hub genes were selected by Maximal Clique Centrality (MCC) method, then the expression and diagnostic value of these hub genes were determined. Consensus clustering algorithm was applied to conduct the unsupervised cluster analysis of the immune-associated hub gene list in IgAN. Finally, the Nephroseq V5 tool was applied to identify the expression level of CCL2, FOS, JUN in kidney diseases, as well as the correlation between CCL2, FOS, JUN expression and renal function in the patients with IgAN.

Results

A total of 129 DEGs were obtained through comparing IgAN with healthy controls via the GSE115857 and GSE35487 datasets. Then, we screened out 24 immune-associated IgAN DEGs. CCL2, JUN, and FOS were identified as the top three hub genes, and they were all remarkably downregulated in IgAN. More importantly, CCL2, JUN, and FOS had a high accuracy [area under the curve (AUC) reached almost 1] in predicting IgAN, which could easily distinguish between IgAN patients and healthy individuals. Three distinct subgroups of IgAN were determined based on 24 immune-associated DEGs, with significant differences in the expression of CCL2, JUN, and FOS genes. Finally, CCL2, FOS, JUN were manifested a meaningful association with proteinuria, glomerular filtration rate (GFR), and serum creatinine level.

Conclusion

In summary, our study comprehensively uncovers that CCL2, JUN, and FOS may function as promising biomarkers for diagnosis of IgAN.

Transmembrane signaling molecules play a key role in the pathogenesis of IgA nephropathy: a weighted gene co-expression network analysis study

BACKGROUND

Immunoglobulin A nephropathy (IgAN) is one of the most common primary glomerulonephritis and a serious health concern worldwide; though still the underlying molecular mechanisms of IgAN are yet to be known and there is no efficient treatment for this disease. The main goal of this study was to explore the IgAN underlying pathogenic pathways, plus identifying the disease correlated modules and genes using the weighted gene co-expression network analysis (WGCNA) algorithm.

RESULTS

GSE104948 dataset (the expression data from glomerular tissue of IgAN patients) was analyzed and the identified differentially expressed genes (DEGs) were introduced to the WGCNA algorithm for building co-expression modules. Genes were classified into six co-expression modules. Genes of the disease's most correlated module were mainly enriched in the immune system, cell-cell communication and transmembrane cell signaling pathways. The PPI network was constructed by genes in all the modules and after hub-gene identification and validation steps, 11 genes, mostly transmembrane proteins (CD44, TLR1, TLR2, GNG11, CSF1R, TYROBP, ITGB2, PECAM1), as well as DNMT1, CYBB and PSMB9 were identified as potentially key players in the pathogenesis of IgAN. In the constructed regulatory network, hsa-miR-129-2-3p, hsa-miR-34a-5p and hsa-miR-27a-3p, as well as STAT3 were spotted as top molecules orchestrating the regulation of the hub genes.

CONCLUSIONS

The excavated hub genes from the hearts of co-expressed modules and the PPI network were mostly transmembrane signaling molecules. These genes and their upstream regulators could deepen our understanding of IgAN and be considered as potential targets for hindering its progression.

Long-term outcomes of IgA nephropathy patients with less than 25% crescents and mild proteinuria

BACKGROUND

Whether immunosuppressive therapy in IgA nephropathy (IgAN) patients with less than 25% crescents (C1) and mild proteinuria can improve the renal outcome is still unclear.

METHODS

We recruited 140 IgAN patients with C1 and proteinuria < 1 g/24 h who received supportive care (n = 52) or steroid-based immunosuppressive therapy (n = 88) in Xijing Hospital from July 2008 to December 2016. The primary outcome was the rate of renal function decline.

RESULTS

The median of proteinuria was 575.5 mg/24 h, the fraction of crescents was 7% (5%, 12%) and follow-up time was 69.1 months. The rate of renal function decline [0.5 (- 1.5, 3.2) vs - 0.7 (- 3.5, 0.5) ml/min per 1.73 m² per year; P = 0.01] was slower in steroid-based immunosuppressive therapy group than supportive care group. Multivariate linear regression analyses showed steroid-based immunosuppressive therapy significantly slowed down the rate of renal function decline (β = - 0.220, 95% CI - 3.804 to - 0.449, P = 0.013) after adjusting age, sex, MAP, proteinuria, eGFR, M1, E1, S1, T1-2, the fraction of crescents and RASB. In the matched cohort, the rate of renal function decline was also slower in steroid-based immunosuppressive therapy group. The incidence of adverse events was similar between the two groups.

CONCLUSION

Steroid-based immunosuppressive therapy may slow down the rate of renal function decline of IgAN patients with C1 and proteinuria ≤ 1 g/24 h.

Spontaneous remission in adult patients with IgA nephropathy treated with conservative therapy

Background

There are few studies describing the clinical course and spontaneous remission of IgA nephropathy (IgAN) in adult patients receiving conservative treatment.

Method

Data from 62 adult patients with biopsy-diagnosed IgAN, who received conservative treatment at least 5 years prior, were retrospectively investigated. No patients received corticosteroids, other immunosuppressants, or tonsillectomy. Remission of proteinuria and hematuria were defined as proteinuria <0.3 g/gCr and urine red blood cells (RBC) <5 / high power field (HPF) on three consecutive urinalyses obtained during an observation period of ≥6 months.

Result

Thirty-eight (61.3%) patients had remission of hematuria, 24 (38.7%) had remission of proteinuria, and 19 (30.6%) had remission of both. Remission rates increased in patients with proteinuria <0.5 g/g Cr at diagnosis. The median time to remission of hematuria was 2.8 years and that of proteinuria was 2.6 years. Patients who showed renal function decline (defined as 30% decline of estimated glomerular filtration rate [eGFR] from baseline) were older, had significantly lower eGFR, and higher proteinuria at diagnosis. Two patients with preserved renal function and normal proteinuria at diagnosis experienced renal function decline. Renal function did not decline within 3 years of diagnosis in patients with proteinuria <1 g/gCr at diagnosis.

Conclusions

Relatively high rates of spontaneous remission were observed. Remission of both hematuria and proteinuria were frequent within 3 years after diagnosis, and renal function was well preserved during this period. These data indicate that it is rational to use conservative treatment for 3 years after the diagnosis instead of aggressive treatments.

Comprehensive analysis of IgA nephropathy expression profiles: identification of potential biomarkers and therapeutic agents

Background

IgA nephropathy (IgAN) is a kidney disease recognized by the presence of IgA antibody depositions in kidneys. The underlying mechanisms of this complicated disease are remained to be explored and still, there is an urgent need for the discovery of noninvasive biomarkers for its diagnosis. In this investigation, an integrative approach was applied to mRNA and miRNA expression profiles in PBMCs to discover a gene signature and novel potential targets/biomarkers in IgAN.

Methods

Datasets were selected from gene expression omnibus database. After quality control checking, two datasets were analyzed by Limma to identify differentially expressed genes/miRNAs (DEGs and DEmiRs). Following identification of DEmiR-target genes and data integration, intersecting mRNAs were subjected to different bioinformatic analyses. The intersecting mRNAs, DEmiRs, related transcription factors (from TRRUST database), and long-non coding RNAs (from LncTarD database) were used for the construction of a multilayer regulatory network via Cytoscape.

Result

“GSE25590” (miRNA) and “GSE73953” (mRNA) datasets were analyzed and after integration, 628 intersecting mRNAs were identified. The mRNAs were mainly associated with “Innate immune system”, “Apoptosis”, as well as “NGF signaling” pathways. A multilayer regulatory network was constructed and several hub-DEGs (Tp53, STAT3, Jun, etc.), DEmiRs (miR-124, let-7b, etc.), TFs (NF-kB, etc.), and lncRNAs (HOTAIR, etc.) were introduced as potential factors in the pathogenesis of IgAN.

Conclusion

Integration of two different expression datasets and construction of a multilayer regulatory network not only provided a deeper insight into the pathogenesis of IgAN, but also introduced several key molecules as potential therapeutic target/non-invasive biomarkers.

Epidemiology, baseline characteristics and risk of progression in the first South-Asian prospective longitudinal observational IgA nephropathy cohort

INTRODUCTION

Glomerular Research And Clinical Experiments-IgA Nephropathy in Indians (GRACE-IgANI) is the first prospective South Asian IgAN cohort with protocolized follow-up and extensive biosample collection. Here we report the baseline clinical, biochemical, and histopathologic characteristics of GRACE IgANI and calculate baseline risk of progression for the cohort.

METHODS

201 incident adults with kidney biopsy-proven primary IgAN were recruited into GRACE-IgANI between March 2015 and September 2017. As of April 30, 2020, the cohort had completed a median follow-up of 30 months (interquartile range [IQR] 16-39).

RESULTS

The commonest clinical presentation in GRACE IgANI was hypertension, with or without proteinuria, and nephrotic-range proteinuria was present in 34%, despite <10 months of lead time to kidney biopsy. The GRACE-IgANI kidney biopsy data demonstrated a disproportionate absence of active glomerular lesions and overrepresentation of segmental sclerosing lesions and tubulointerstitial fibrosis at presentation, often coexistent with relatively well-preserved estimated glomerular filtration rate (eGFR) and low levels of proteinuria, especially in males. Baseline risk of progression was calculated for each evaluable patient using 2 different risk prediction tools. The median 5-year absolute risk of end-stage kidney disease (ESKD) was 19.8% (IQR 2.7-57.4) and median 5-year risk of progression to the combined endpoint of 50% decline in eGFR or ESKD was 35.5% using the 2 tools.

CONCLUSIONS

The predicted risk of progression in this cohort was considerable. Over the next 5 years, we will dissect the pathogenic pathways that underlie this severe South Asian IgAN phenotype.

Urinary cMet as a prognostic marker in immunoglobulin A nephropathy

The prediction of prognosis in patients with immunoglobulin A nephropathy (IgAN) is challenging. We investigated the correlation between urinary cMet (ucMet) levels and clinical parameters and examined the effects of cMet agonistic antibody (cMet Ab) in an in vitro IgAN model. Patients diagnosed with IgAN (n = 194) were divided into three groups representing undetectable (Group 1), below‐median (Group 2) and above‐median (Group 3) levels of ucMet/creatinine (ucMet/Cr). Stained kidney biopsy samples were graded according to cMet intensity. Primary‐cultured human mesangial cells were stimulated with recombinant tumour necrosis factor (TNF)‐α and treated with cMet Ab. Our results showed that ucMet/Cr levels positively correlated with proteinuria (P < .001). During the follow‐up, patients in Group 3 showed a significantly lower probability of complete remission (CR; uPCr < 300 mg/g) than those in groups 1 and 2, after adjusting for blood pressure, estimated glomerular filtration rate, and proteinuria, which influence clinical prognosis (HR 0.60, P = .038); moreover, ucMet/Cr levels were also associated with glomerular cMet expression. After TNF‐α treatment, the proliferation of mesangial cells and increased interleukin‐8 and intercellular adhesion molecule‐1 expression were markedly reduced by cMet Ab in vitro. In conclusion, ucMet/Cr levels significantly correlated with proteinuria, glomerular cMet expression, and the probability of CR. Further, cMet Ab treatment alleviated the inflammation and proliferation of mesangial cells. Hence, ucMet could serve as a clinically significant marker for treating IgAN.

The role of hypertriglyceridemia and treatment patterns in the progression of IgA nephropathy with a high proportion of global glomerulosclerosis

PURPOSE

Many studies have focused on finding predictors for mild IgAN progression. However, the cases of severe IgAN with a high proportion of global glomerulosclerosis have received inadequate attention.

METHODS

A group of 172 primary IgAN patients with 50-75% global glomerulosclerosis was studied retrospectively between April 2007 and October 2017. Patients were divided into three groups according to the serum triglyceride tertiles:  < 1.42 µmol/L (Group 1), 1.42-2.29 µmol/L (Group 2), and > 2.29 µmol/L (Group 3). Groups 1 and 2 comprised non-hypertriglyceridemia subjects, while Group 3 was defined as the hypertriglyceridemia (HTG) group. The patients were followed for 4-96 months (median 39.43 months). The study end point was defined as a 50% decline in estimated glomerular filtration rate (eGFR) or ESRD.

RESULTS

A high proportion of global glomerulosclerosis is not absolutely correlated with severe clinical features and poor renal outcome. In our retrospective observation, eGFR decreased by less than 10% of the baseline during follow-up in 43.6% of the patients. However, in our patients with HTG, the cumulative renal survival rate was significantly lower compared to those without HTG. Multivariate Cox regression analysis also showed that triglyceride is an independent predictor of poor renal outcomes. Furthermore, in the HTG group, the cumulative renal survival rates were higher in patients treated with Tripterygium wilfordii Hook F (TwHF) compared to those without TwHF.

CONCLUSIONS

A high proportion of global glomerulosclerosis combined with HTG at biopsy have better predictive validity for the disease progression of IgAN than global glomerulosclerosis alone. TwHF may partially affect the renal outcome of severe IgAN with HTG, and this may relate to its regulation of lipid metabolism and immunoinflammatory response.

Clinical impact of endocapillary proliferation with modified cutoff points in IgA nephropathy patients

Predictive values of mesangial proliferation (M), endocapillary proliferation (E), segmental glomerulosclerosis (S), and crescents (C) among 19 validation studies of the Oxford Classification of IgA nephropathy (IgAN) were discrepant, especially in Asian patients. These validation studies indicate that cutoffs of MESC score in the Oxford Classification may not be generalizable. Thus, we aimed to improve the clinical value of MESC scores by modifying the cutoff points. A total of 104 patients with IgAN were diagnosed from 2001 to 2012 vai renal biopsy and retrospectively evaluated at Nagoya University Hospital. The cutoff point for modified (M´E´S´C´) was determined using the receiver operating characteristic curve in association with renal outcome in the training cohort. Clinical values of the Oxford MESTC vs M´E´S´C´ cutoff points were analyzed using Kaplan-Meier and Cox regression in association with poor renal outcome in the validation and the entire cohort. Of 104 patients, 12.5% reached poor renal outcome over a median of 6.25 [4.16–9.61] years of follow-up. The modified cutoffs were defined as ≥40%, ≥10%, ≥20%, and ≥5% in the glomeruli for M´E´S´, and C´ respectively. In univariate analysis, E´, S ´, and T were significantly associated with poor renal outcome, whereas Oxford MESC, M´, and C´ in the training and validation cohort were not associated with poor renal outcome. Using multivariate analysis in the presence of estimated glomerular filtration rate (eGFR), only E´ was a significant predictive factor for poor renal outcome. The E´ with modified cutoff point of 10% significantly improved predictive value for poor renal outcome in IgAN. Therefore, the clinical value of modified cutoff points for M´E´S´C´ scores should be validated with various cohort studies in different regions.

Clinical Significance of Crescent Formation in IgA Nephropathy – a Multicenter Validation Study

Background/Aims: Additional validation study was warranted to confirm the clinical significance of C score, which was recently added to the Oxford classification for immunoglobulin A nephropathy (IgAN). Methods: We performed a multicenter retrospective cohort study in four hospitals in Korea. Patients who had biopsied glomeruli less than eight or inadequate follow-up information were excluded. Clinicopathologic parameters, including the degree of cellular or fibrocellular crescents, were collected and included in multivariable models for Cox regression analysis. The main outcome was a composite renal outcome, defined as a merge of progression to end-stage renal disease (ESRD) and halving of estimated glomerular filtration rate (eGFR) from baseline. Results: Among included 3,380 biopsy-confirmed IgAN patients, there were 664 (19.6%) patients with C1 and 60 (1.8%) patients with C2 scores in the study population. Although C0 and C1 patients shared similar baseline characteristics, C2 patients frequently had more clinicopathologic risk factors for poor prognosis of IgAN. Both C1 [adjusted HR 1.33 (1.11-1.58), P=0.002] and C2 [adjusted HR 2.24 (1.46-3.43), P< 0.001] scores were associated with an increased risk of the composite outcome. C2 was a strong predictive parameter associated with both progression to ESRD and halving of eGFR, whereas C1 was mainly associated with the increased risk of halving of eGFR. Notably, the proportion of crescent showed a linear association with the risk of adverse renal outcome. Conclusion: The C score in the Oxford classification is a valid predictive parameter for IgAN prognosis. Additional clinical attention is necessary for IgAN patients with identified cellular or fibrocellular crescents.

A Systematic Review on Materno-Foetal Outcomes in Pregnant Women with IgA Nephropathy: A Case of "Late-Maternal" Preeclampsia?

Background: IgA nephropathy is the most common primary glomerulonephritis in pregnancy and shares with other immunologic diseases and kidney diseases a relationship with adverse maternal outcomes, whose entity and pattern is only partially quantified. Recent studies provide new information and a systematic review regarded progression of kidney disease. The discussion of the outcomes with respect to low-risk pregnancies may help to perfect the estimation of the risks, and to identify specific research needs. Methods: A search strategy was built on Medline, EMBASE and the Cochrane review for the period January 2000–April 2017, aimed at retrieving both case series (defined as with at least 6 pregnancies in women with IgA nephropathy) and case reports, to look into rare occurrences. All papers, with or without control groups, were selected if they reported on at least one pregnancy outcome, or on long-term kidney function. Search strategy, paper selection and data extraction were done in duplicate (PROSPERO N 42016042623). Meta-analysis of case series was performed with Metanalyst Beta 3.13. Case reports were analysed narratively. Results: The search retrieved 556 papers, of which 27 were included (13 series and 14 case-reports). The case series report on 581 women with 729 pregnancies. The analysis was performed in comparison to the available control groups: 562 non-pregnant controls were available for the analysis of progression of kidney disease. As for pregnancy related outcomes (preeclampsia (PE), pregnancy induced hypertension (PIH), preterm birth, small babies), we meta-analyzed the data with respect to the only series of low-risk pregnancies (1418 pregnancies). When compared with women who never got pregnant after diagnosis of IgA nephropathy, in the present meta-analysis pregnancy in women with IgA nephropathy was not associated with a higher risk of progression of kidney disease, possibly due to the overall preserved kidney function at baseline: end-stage kidney disease (OR 0.68; CI 0.28–1.65). Conversely, the incidence of adverse pregnancy-related outcomes was increased compared to low-risk controls: PE and PIH were more than ten-fold increased (OR 11.80; CI 7.53–18.48 and OR 10.39; CI 5.45–19.80), while the increase in risk of preterm birth and “low birth weight babies” was less marked (OR 3.37; CI 1.91–5.95 and OR 2.36; CI 1.52–3.66), a discrepancy suggesting the occurrence of “late” or “maternal” PE, that may affect less severely foetal growth or shorten gestation. In conclusion, in the present meta-analysis IgA nephropathy was not associated with an increased progression of kidney disease. The more than ten-fold increased risk of PIH and PE, in combination with a doubled risk of small babies, suggests the occurrence of “late” or “maternal” PE, usually less affecting early foetal growth. This finding may be of help in defining control policies, while further research is needed to guide clinical management.

Association between serum albumin level and incidence of end-stage renal disease in patients with Immunoglobulin A nephropathy: A possible role of albumin as an antioxidant agent

Serum albumin is the major intravascular antioxidant. Though oxidative stress plays an important role in the pathophysiology of Immunoglobulin A nephropathy (IgAN), the association between serum albumin and the progression of IgAN is not entirely understood. This retrospective cohort study of 1,352 participants with biopsy-proven IgAN determined the associations between serum albumin level and the incidence of end-stage renal disease (ESRD) using a Cox proportional hazards model. Patients were divided into three groups by tertiles of serum albumin level: Low, Middle, and High group (≤3.9 g/dL, 4.0–4.3 g/dL, ≥4.4 g/dL, respectively). During the median 5.1-year follow-up period, 152 patients (11.2%) developed ESRD. Participants in the Low group had a 1.88-fold increased risk for ESRD compared with those in the High group after adjustment for clinical parameters, including urinary protein excretion, and pathological parameters (Oxford classification). We also experimentally proved the antioxidant capacity of albumin on mesangial cells. The intracellular reactive oxygen species and mitochondrial injury, induced by hydrogen peroxide were significantly attenuated in albumin-pretreated mouse mesangial cells and human kidney cells compared with γ-globulin-pretreated cells. Low serum albumin level is an independent risk factor for ESRD in patients with IgAN. The mechanism could be explained by the antioxidant capacity of serum albumin.

Clinical dissection of thrombotic microangiopathy

Differential treatment strategies are applied in thrombotic microangiopathy (TMA) according to the sub-classifications. Hence, it is worthwhile to overview clinical manifestations and outcomes of overall TMA patients according to sub-classifications. We analyzed TMA patients whose serum lactate dehydrogenase levels >250 IU/L, with the presence of schistocytes in their peripheral blood smear, or with typical vascular pathologic abnormalities in their renal biopsy. We compared clinical manifestations including overall survival (OS) and renal survival according to TMA causes. A total of 117 TMA patients (57 primary and 60 secondary TMA) were analyzed. Renal symptom was the most common manifestation in whole patients, while renal function at diagnosis was worst in pregnancy-related TMA group. Primary TMA patients had more frequent CNS symptom and hematologic manifestation compared to secondary TMAs. Among secondary TMAs, pregnancy- and HSCT-related TMA patients showed prevalent hemolytic features. During 150.2 months of follow-up, 5-year OS rate was 64.8%. Poor prognostic factors included older age, combined hematologic and solid organ malignancies, lower hemoglobin levels, and lower serum albumin levels. There was no significant difference in OS between primary and secondary TMAs. Seventy-eight percent of patients experienced AKI during TMA. Five-year death-censored renal survival rate was poor with only 69.2%. However, excellent renal outcome was observed in pregnancy-associated TMA. TMA showed various clinical manifestations according to their etiology. Notably, both OS and renal survival were poor regardless of their etiologies except pregnancy-associated TMA. Physicians should differentiate a variety of TMA categories and properly manage this complex disease entity.

The Japanese Histologic Classification and T-score in the Oxford Classification system could predict renal outcome in Japanese IgA nephropathy patients

BACKGROUND

The Oxford Classification is utilized globally, but has not been fully validated. In this study, we conducted a comparative analysis between the Oxford Classification and Japanese Histologic Classification (JHC) to predict renal outcome in Japanese patients with IgA nephropathy (IgAN).

METHODS

A retrospective cohort study including 86 adult IgAN patients was conducted. The Oxford Classification and the JHC were evaluated by 7 independent specialists. The JHC, MEST score in the Oxford Classification, and crescents were analyzed in association with renal outcome, defined as a 50% increase in serum creatinine.

RESULTS

In multivariate analysis without the JHC, only the T score was significantly associated with renal outcome. While, a significant association was revealed only in the JHC on multivariate analysis with JHC.

CONCLUSIONS

The JHC and T score in the Oxford Classification were associated with renal outcome among Japanese patients with IgAN. Superiority of the JHC as a predictive index should be validated with larger study population and cohort studies in different ethnicities.

Evaluation of TGF-β1 and MCP-1 expression and tubulointerstitial fibrosis in children with Henoch-Schönlein purpura nephritis and IgA nephropathy: A clinical correlation

OBJECTIVES:

Henoch-Schönlein purpura nephritis and immunoglobulin A nephropathy are two diseases with similar clinical presentations but very different prognoses. Transforming growth factor β1 and monocyte chemoattractant protein-1 have been associated with the development of tissue fibrosis. We examined the development of tubulointerstitial fibrosis and its relationship with Transforming growth factor β1 and monocyte chemoattractant protein-1 expression in these patients.

METHODS:

Renal tissue samples were collected by renal biopsy from 50 children with Henoch-Schönlein purpura nephritis and 50 children with immunoglobulin A nephropathy. Hematoxylin and eosin and Masson's trichrome-stained tissues were examined using light microscopy. Tubulointerstitial fibrosis was graded using the method described by Bohle et al. (1). The immunohistochemical detection of Transforming growth factor β1 and monocyte chemoattractant protein-1 expression was correlated with the tubulointerstitial fibrosis grade. Clinical Trial registration number: ZJCH-2012-0105.

RESULTS:

Transforming growth factor β1 and monocyte chemoattractant protein-1 expression in the renal tissues was significantly greater in the patients with immunoglobulin A nephropathy than in the patients with Henoch-Schönlein purpura nephritis (both p<0.001). The immunoglobulin A nephropathy patients had a higher tubulointerstitial fibrosis grade than the Henoch-Schönlein purpura nephritis patients (p<0.001). The tubulointerstitial fibrosis grade was in accordance with the Transforming growth factor β1 and monocyte chemoattractant protein-1 expression levels in both diseases (both p<0.001).

CONCLUSION:

Transforming growth factor β1 and monocyte chemoattractant protein-1 expression was associated with the development of immunoglobulin A nephropathy and Henoch-Schönlein purpura nephritis. Further studies are needed to better evaluate this association.

Why, when and how should immunosuppressive therapy considered in patients with immunoglobulin A nephropathy?

IgA nephropathy (IgAN) is the most common primary glomerulonephritis worldwide. Lifelong mesangial deposition of IgA1 complexes subsist inflammation and nephron loss, but the complex pathogenesis in detail remains unclear. In regard to the heterogeneous course, classical immunosuppressive and specific therapeutic regimens adapted to the loss of renal function will here be discussed in addition to the essential common renal supportive therapy. Renal supportive therapy alleviates secondary, surrogate effects or sequelae on renal function and proteinuria of high intraglomerular pressure and subsequent nephrosclerosis by inhibition of the renin angiotensin system (RAASB). In patients with physiological (ΔGFR < 1·5 ml/min/year) or mild (ΔGFR 1·5-5 ml/min/year) decrease of renal function and proteinuric forms (> 1 g/day after RAASB), corticosteroids have shown a reduction of proteinuria and might protect further loss of renal function. In patients with progressive loss of renal function (ΔGFR > 3 ml/min within 3 months) or a rapidly progressive course with or without crescents in renal biopsy, cyclophosphamide with high-dose corticosteroids as induction therapy and azathioprine maintenance has proved effective in one randomized controlled study of a homogeneous cohort in loss of renal function (ΔGFR). Mycophenolic acid provided further maintenance in non-randomized trials. Differentiated, precise, larger, randomized, placebo-controlled studies focused on the loss of renal function in the heterogeneous forms of IgAN are still lacking. Prospectively, fewer toxic agents will be necessary in the treatment of IgAN.

Corticosteroids in IgA Nephropathy: Lessons from Recent Studies

IgA nephropathy (IgAN) is a common chronic glomerular disease that, in most patients, slowly progresses to ESRD. The immune and autoimmune responses that characterize IgAN indicate a potential benefit for corticosteroids. The 2012 Kidney Disease Improving Global Outcome (KDIGO) guidelines suggest giving corticosteroids to patients with rather preserved renal function (GFR>50 ml/min per 1.73 m²) and persistent proteinuria >1 g/d, despite 3-6 months of optimized supportive care with renin-angiotensin system blockers. However, the evidence supporting this guideline was considered of low quality. More recent results from large cohort studies and randomized, controlled trials have provided conflicting messages about the benefits of corticosteroid treatment over supportive care alone, mostly involving optimized renin-angiotensin system blockade, which might generate further uncertainty in the therapeutic choice. Overall, these results indicate that corticosteroids are a powerful tool for treating patients with IgAN; however, treatment success is not universal and mostly occurs in patients who are highly proteinuric with early CKD. In patients with advanced CKD, the side effects of corticosteroids increase, and the renal protection decreases. This brief review aimed at integrating the findings of these recently published reports to provide balanced advice for clinicians as well as suggestions for future trials.

The urine albumin-to-creatinine ratio is a reliable indicator for evaluating complications of chronic kidney disease and progression in IgA nephropathy in China

OBJECTIVE

This study investigated the correlation between the albumin-to-creatinine ratio in the urine and 24-hour urine proteinuria and whether the ratio can predict chronic kidney disease progression even more reliably than 24-hour proteinuria can, particularly in primary IgA nephropathy.

METHODS

A total of 182 patients with primary IgA nephropathy were evaluated. Their mean urine albumin-to-creatinine ratio and 24-hour proteinuria were determined during hospitalization. Blood samples were also analyzed. Follow-up data were recorded for 44 patients. A cross-sectional study was then conducted to test the correlation between these parameters and their associations with chronic kidney disease complications. Subsequently, a canonical correlation analysis was employed to assess the correlation between baseline proteinuria and parameters of the Oxford classification. Finally, a prospective observational study was performed to evaluate the association between proteinuria and clinical outcomes. Our study is registered in the Chinese Clinical Trial Registry, and the registration number is ChiCTR-OCH-14005137.

RESULTS

A strong correlation (r=0.81, p<0.001) was found between the ratio and 24-hour proteinuria except in chronic kidney disease stage 5. First-morning urine albumin-to-creatinine ratios of ≥125.15, 154.44 and 760.31 mg/g reliably predicted equivalent 24-hour proteinuria 'thresholds' of ≥0.15, 0.3 and 1.0 g/24 h, respectively. In continuous analyses, the albumin-to-creatinine ratio was significantly associated with anemia, acidosis, hypoalbuminemia, hyperphosphatemia, hyperkalemia, hypercholesterolemia and higher serum cystatin C. However, higher 24-hour proteinuria was only associated with hypoalbuminemia and hypercholesterolemia. Higher tubular atrophy and interstitial fibrosis scores were also associated with a greater albumin-to-creatinine ratio, as observed in the canonical correlation analysis. Finally, the albumin-to-creatinine ratio and 24-hour proteinuria were associated with renal outcomes in univariate analyses.

CONCLUSION

This study supports the recommendation of using the albumin-to-creatinine ratio, rather than 24-hour proteinuria, to monitor proteinuria and prognosis in primary IgA nephropathy.

Long-term prognosis of IgA nephropathy presenting with minimal or no proteinuria: A single center experience

The long-term prognosis of patients with IgA nephropathy (IgAN) who present with preserved renal function and minimal proteinuria is not well described. We investigated the long-term outcomes of IgAN patients with an apparently benign presentation and evaluated prognostic factors for renal survival and clinical remission. We studied Japanese patients with biopsy-proven IgAN who had an estimated glomerular filtration rate (eGFR) ≥60 mL/min/1.73 m² and proteinuria <0.5 g/day at the time of renal biopsy. The renal biopsies were reviewed using the Oxford classification. Twenty patients met the inclusion criteria. At diagnosis, the median eGFR (interquartile range) was 76.8 (65.2–91.1) mL/min/1.73 m², and the median proteinuria level was 0.31 (0.16–0.39) g/day. Only one patient had an increase in serum creatinine of over 50% and no patient progressed to end-stage renal disease. The 15-year renal survival rate was 93.8%. Clinical remission was observed in 9 (45%) patients. Baseline proteinuria was the only factor significantly associated with the absence of clinical remission. The long-term prognosis of Japanese patients with IgAN who presents with minor urinary abnormalities and preserved renal function is excellent.

Predictors of Relapse in Adult-Onset Nephrotic Minimal Change Disease

Minimal change disease (MCD) is a well-known benign primary glomerulonephritis because of its distinct rare tendency to progress to end-stage renal disease. However, factors associated with relapse in adults are not well known. We aimed to identify predictors of relapse in adult-onset MCD patients.A retrospective cohort of 195 patients with adult-onset primary MCD with nephritic syndrome and disease onset between 1979 and 2013 was followed up for >12 months. The number of relapses was counted and predictors of relapse were analyzed.A total of 195 patients were included. Median age at diagnosis was 38 years (IQR, 23-53 years) and 113 (57.9%) were men. During 81 months (IQR, 44-153 months) of follow-up, 92% of patients achieved remission after initial treatment. However, only 60 (32.8%) did not experience a relapse and 11 patients failed to remit. Among the remaining 124 patients, 65 experienced a relapse once or twice and 59 experienced a relapse more than twice. Younger onset age, increased severity of nephrotic features such as lower serum albumin levels and higher cholesterol level were associated with relapse. Interestingly, the grade of mesangial proliferation was lower in patients who experienced a relapse. Initial combined treatment with corticosteroids (CS) and cyclophosphamide reduced the number of relapses. In addition, patients with shorter treatment duration tended to experience relapse more often. Multivariate analysis showed that younger onset age, combined mesangial proliferation, initial treatment regimen, and treatment duration were independent risk factors for relapse. Progression to end-stage renal disease was developed in only a patient.In conclusion, more than two-thirds of adult-onset nephrotic MCD patients experienced relapse, although their renal progression was rare. Younger onset age, CS without cyclophosphamide treatment, and shorter treatment duration were independent risk factors for relapse in adult-onset MCD patients.

IgA nephropathy

Globally, IgA nephropathy (IgAN) is the most common primary glomerulonephritis that can progress to renal failure. The exact pathogenesis of IgAN is not well defined, but current biochemical and genetic data implicate overproduction of aberrantly glycosylated IgA1. These aberrant immunoglobulins are characterized by galactose deficiency of some hinge-region O-linked glycans. However, aberrant glycosylation alone is insufficient to induce renal injury: the participation of glycan-specific IgA and IgG autoantibodies that recognize the undergalactosylated IgA1 molecule is required. Glomerular deposits of immune complexes containing undergalactosylated IgA1 activate mesangial cells, leading to the local overproduction of cytokines, chemokines and complement. Emerging data indicate that mesangial-derived mediators that are released following mesangial deposition of IgA1 lead to podocyte and tubulointerstitial injury via humoral crosstalk. Patients can present with a range of signs and symptoms, from asymptomatic microscopic haematuria to macroscopic haematuria. The clinical progression varies, with 30-40% of patients reaching end-stage renal disease 20-30 years after the first clinical presentation. Currently, no IgAN-specific therapies are available and patients are managed with the aim of controlling blood pressure and maintaining renal function. However, new therapeutic approaches are being developed, building upon our ever-improving understanding of disease pathogenesis.

Sequential therapy with cyclophosphamide and mycophenolic acid in patients with progressive immunoglobulin A nephropathy: a long-term follow-up

In progressive immunoglobulin (Ig)A nephropathy (IgAN), cyclophosphamide pulse therapy (CyP), high-dose intravenous immunoglobulins (IVIg) and mycophenolic acid (MPA) have been used to stop progressive loss of renal function, but disease progression may occur after the end of the initial treatment. Here, we report the long-term follow-up of patients with progressive IgAN with MPA as maintenance therapy after CyP (CyP-MPA). In a median observation time of 6·2 years, we analysed the slopes of the loss of renal function of 47 patients with biopsy-proven IgAN and treated with CyP. Thirty-one patients with further progression were treated with MPA maintenance for a median time of 5·2 years. Follow-up was compared with symptomatic therapy and IVIg as historically matched control groups. Median loss of renal function was reduced significantly from 0·9 ml/min to 0·1 ml/min per month with CyP (P < 0·05), and with MPA in patients with a relapse from -0·4 ml/min to -0·1 ml/min per month (P < 0·05) until the end of the study. Proteinuria decreased significantly from 1·6 g/l to 1·0 g/l after CyP, and during MPA treatment to 0·6 g/l (P = 0·001 Friedman test). Median renal survival time was in patients with CyP 10·5 years (range = 3·2-17·8), with CyP-MPA 10·7 years (range = 8·3-13·1), with IVIg 4·7 years (range = 2·6-6·6), and in untreated patients 1·2 years (range = 0·8-1·6; log-rank test P < 0·01). In patients with progressive IgAN, our long-term follow-up observation indicates that sequential CyP-MPA therapy maintains renal survival significantly.

New developments in the genetics, pathogenesis, and therapy of IgA nephropathy

Recent years have brought notable progress in the field of IgA nephropathy. Here, we highlight important new directions and latest developments, including successful discovery of several genetic susceptibility loci, formulation of the multihit pathogenesis model, introduction of the Oxford pathology scoring system, and formalization of the Kidney Disease Improving Global Outcomes (KDIGO) consensus treatment guidelines. We focus on the latest genetic findings that confirm a strong contribution of inherited factors and explain some of the geoethnic disparities in disease susceptibility. Most IgA nephropathy susceptibility loci discovered to date encode genes involved in the maintenance of the intestinal epithelial barrier and response to mucosal pathogens. The concerted pattern of interpopulation allelic differentiation across all genetic loci parallels the disease prevalence and correlates with variation in local pathogens, suggesting that multilocus adaptation might have shaped the present-day landscape of IgA nephropathy. Importantly, the 'Intestinal Immune Network for IgA Production' emerged as one of the new targets for potential therapeutic intervention. We place these findings in the context of the multihit pathogenesis model and existing knowledge of IgA immunobiology. Lastly, we provide our perspective on the existing treatment options, discuss areas of clinical uncertainty, and outline ongoing clinical trials and translational studies.

Significance of tonsillectomy combined with steroid pulse therapy for IgA nephropathy with mild proteinuria

Background

Medical intervention for patients with IgA nephropathy and mild proteinuria (<1.0 g/day) is controversial, and the effectiveness of tonsillectomy plus steroid pulse therapy (TSP) for such patients remains obscure.

Methods

Among 323 patients in our multicenter cohort study, 79 who had mild proteinuria (0.4–1.0 g/day) at diagnosis were eligible to participate in this study. We compared the clinicopathological findings at diagnosis, a decline in renal function defined as a 50 or 100 % increase in serum creatinine (sCr) and clinical remission (CR) defined as the disappearance of hematuria and proteinuria (<0.3 g/day) among groups given TSP (n = 46), steroid therapy (ST) (n = 9), and non-ST (n = 24). Factors contributing to CR were also evaluated using multivariate analysis.

Results

Background factors at diagnosis including age, ratio (%) of patients with hypertension, sCr, proteinuria, and histological severity did not significantly differ among the groups. Only two patients each in the TSP (4.3 %) and non-ST (8.3 %) groups achieved a 50 % increase in sCr during a mean follow–up period of 4.7 years. At the final observation, 71.7, 44.4, and 41.7 % of patients in the TSP, ST, and non-ST groups, respectively, achieved CR (p = 0.032). Cox proportional hazards models revealed that TSP led to CR more effectively than non-TSP by a factor of about threefold (hazard ratio, 2.74; p = 0.008).

Conclusion

TSP therapy has potential for inducing CR in patients with IgAN and mild proteinuria (<1.0 g/day).

Renal biopsy findings and clinical indicators of patients with hematuria without overt proteinuria

Background

Whether to perform a renal biopsy for isolated hematuria remains a matter of controversy. We performed renal biopsy in hematuria without overt proteinuria patients and reported the proportion of glomerulonephritis, pathological activities, and statistical analysis of indicators associated with glomerulonephritis.

Methods

Among 203 patients who underwent renal biopsy in Okubo Hospital, Japan, between January 2008 and October 2013, we identified 56 patients who fulfilled the criteria: (1) urine dipstick examination shows equal to or greater than ± blood on three or more visits, (2) proteinuria <0.3 g/day (g/g Cr), (3) eGFR ≧60 ml/min/1.73 m², and (4) no current medication for renal disease. We investigated biopsy findings and compared the clinical indicators in the IgA nephropathy (IgAN) and non-IgAN group.

Results

The pathological diagnosis was IgAN in 35 cases (62 %), thin basement membrane disease (TBMD) in 7 (13 %), minor glomerular abnormality (MGA) in 6 (11 %), glomerular basement membrane (GBM) abnormality in 5 (9 %), and others in 3 (5 %). The histological grade of IgAN was I in 90 % and II in 10; 31 % of patients had some crescentic lesions. Comparisons between the IgAN and non-IgAN group revealed significant differences in age of onset (26 ± 13 vs. 34 ± 17 years, p = 0.04), serum IgA (340 ± 114 vs. 220 ± 101 mg/dl, p < 0.01), proteinuria (0.08 [0–0.25] vs. 0 [0–0.23] g/day [g/gCr], p < 0.01), and the presence of poikilocytes (40 vs. 10 %, p = 0.02).

Conclusions

The proportion of IgAN in hematuria without overt proteinuria was high and the pathological activities were variable. Patients with hematuria without overt proteinuria should continue their medical follow-up and the best timing of biopsy may be controversial for these patients who have multiple risk factors of IgAN.