An evaluation of the roles of hematuria and uric acid in defining the prognosis of patients with IgA nephropathy

Is Childhood IgA Nephropathy Different From Adult IgA Nephropathy? A Narrative Review

Purpose of the review

Immunoglobulin A (IgA) nephropathy (IgAN) is the most common primary glomerular kidney disease. Children and adults are presumed to have the same disease and are treated similarly. However, there are differences between childhood IgAN and adult IgAN that may require unique treatment considerations, even after transition to adult nephrology services. A narrative review was conducted to compare childhood and adult IgAN and to describe the distinct characteristics of childhood IgAN. Reframing childhood IgAN can inform guideline recommendations unique to childhood IgAN, the development of targeted therapies, and clinical trial design.

Sources of information

Medline and Embase were searched for reports on children and adults with IgAN published between January 2013 and December 2023 (updated May 2024). The search was not restricted by age group, outcomes reported, language, or study design. Randomized controlled trials (RCTs), observational studies, review articles, and nephrology conference abstracts were included. A total of 3104 reports were retrieved. Forty-seven reports (37 primary studies and 10 reviews) were included in the review. Two RCTs and 35 observational studies included a total of 45 085 participants (9223 children and 35 862 adults).

Method

Data were extracted for primary IgAN and not for IgA vasculitis-associated nephritis. Findings were described with no statistical comparisons due to variations in interventions and outcome definitions.

Key findings

Gross hematuria was the obvious clinical difference between childhood IgAN and adult (60-88% vs 15-20%). Nephrotic syndrome was more common in children, approaching up to 44%, while <18% of adults had nephrotic syndrome. Children were biopsied sooner (6 vs 15 months) and had more inflammatory kidney lesions (mesangial hypercellularity: 41-82% vs 38-64%; endocapillary hypercellularity: 39-58% vs 17-34%). Chronic kidney lesions were more prevalent in adults (segmental sclerosis: 62-77% vs 8-51%; interstitial fibrosis/tubular atrophy: 34-37% vs 1-18%). The use of immunosuppressive therapy was higher in children (46-84% vs 35-56%). Children were started on immunosuppressive therapy sooner than adults. Adults were more likely to be optimized with renin-angiotensin system inhibitors (87-94% vs 49-75%). Children had better kidney function than adults at diagnosis (estimated glomerular filtration rate of 90-128 vs 50-88 ml/min/1.73 m2), and children also had better kidney survival, with kidney failure of 3.1% vs 13.4% at 5 years. Children had more risk alleles for IgAN and higher levels of mannose-binding lectin than adults.

Limitations

Most studies were retrospective and observational, with limited data on children and disease mechanisms. Data were not pooled for analysis because of important differences in definitions and measurements of baseline characteristics and outcomes. Data from countries with established urine screening programs were different compared to countries without urine screening programs. Some observed differences may be due to practice variation and delayed diagnosis in adults (lead-time bias). Well-designed prospective studies and standardized measures for kidney function assessment and outcomes can reduce heterogeneity and improve results from reviews.

Conclusion

Inherent differences between childhood IgAN and adult IgAN may be due to distinct disease mechanisms. Approaching childhood IgAN as a separate condition could lead to the discovery of targeted therapies and improve management during childhood and after the transition to adult care.

Machine learning-based unsupervised phenotypic clustering analysis of patients with IgA nephropathy: Distinct therapeutic responses of different groups

BACKGROUND

Immunoglobulin A nephropathy (IgAN) has a heterogeneous clinical presentation. Comparison of different IgAN subgroups may facilitate the application of more targeted therapies. This study was aimed to distinct disease phenotypes in IgAN and to develop prognostic models for renal composite outcomes.

METHODS

Clinical and pathological data were from 2000 patients with biopsy-proven primary IgAN from four centers, including the First Affiliated Hospital of Sun Yat-sen University (SYSU), the Fifth Affiliated Hospital of Sun Yat-sen University, the Huadu District People's Hospital of Guangzhou, and Jieyang Affiliated Hospital of SYSU in China between January 2009 and December 2018 (training cohort: 1203 patients, validation cohort: 797 patients). Components from principal components analysis (PCA) were used to fit a k-means clustering algorithm and identify distinct subgroups. A subgroup-based prediction model was developed to assess prognosis and therapeutic efficacy in each subgroup.

RESULTS

The PCA-k-means clustering algorithm identified four subgroups. Subgroup 1 had significantly better long-term renal survival upon administration of a renin-angiotensin system blocker (adjusted hazard ratio [aHR]: 0.16, 95% confidence interval [CI]: 0.10-0.27, P <0.001). Subgroup 2 had a significant improvement from corticosteroid therapy (aHR: 0.19, 95% CI: 0.06-0.61, P = 0.005). Subgroups 3 and 4 had milder pathological changes and relatively stable kidney function for several years. Subgroup 3 (predominantly males) had a high incidence of metabolic risk factors, necessitating more intensive monitoring; subgroup 4 (predominantly females) had a high incidence of recurrent macroscopic hematuria. These patterns were similar in the validation cohort. A subgroup-based prognosis prediction model demonstrated an area under the curve of 0.856 in the validation dataset.

CONCLUSION

The unsupervised clustering method provided reliable classification of IgAN patients into different subgroups according to clinical features, prognoses, and treatment responsiveness. Our subgroup-based prediction model has significant clinical utility for the assessment of risk and treatment in patients with IgAN.

IPNA clinical practice recommendations for the diagnosis and management of children with IgA nephropathy and IgA vasculitis nephritis

IgA nephropathy and IgA vasculitis with nephritis, albeit rare, represent two relatively frequent glomerular conditions in childhood. Compared to adults, pediatric IgA nephropathy has a more acute presentation, most frequently with synpharyngitic macrohematuria and histologically with more intense inflammation and less intense chronic damage. Management of these conditions is controversial and supported by little high-quality evidence. The paucity of evidence is due to the disease heterogeneity, its inter-ethnic variability, and the difficulty of extrapolating data from adult studies due to the peculiarities of the condition in children. IgA vasculitis with nephritis is a kidney manifestation of a systemic disorder, typical of the pediatric age, in which both the diagnosis of kidney involvement and its management are poorly defined, and an interdisciplinary approach is crucial. Both conditions can have a profound and long-lasting impact on kidney function and the global health of affected children. The International Pediatric Nephrology Association has therefore convened a diverse international group of experts from different disciplines to provide guidance on the recommended management of these conditions in children and to establish common definitions and define priorities for future high-quality, evidence-based collaborative studies for the benefit of children.

The Relationship between Vascular Biomarkers (Serum Endocan and Endothelin-1), NT-proBNP, and Renal Function in Chronic Kidney Disease, IgA Nephropathy: A Cross-Sectional Study

IgA nephropathy (IgAN) is the most common primary glomerular disease. Endothelin-1 (ET-1) is one of the strongest vasoconstrictor materials in the blood. The N-terminal prohormone of brain natriuretic peptide (NT-proBNP) is associated with renal function and poor outcomes in chronic kidney disease (CKD). Serum endocan is a biomarker associated with proinflammatory cytokines, and the increase in the serum level plays a critical role in inflammatory, proliferative, and neovascularization processes and is associated with poor cardiovascular outcomes in patients with CKD too. Identifying high-risk patients using biomarkers could help to optimize their treatment. Ninety patients with biopsy-confirmed IgAN were included in the study (50 males/40 females, mean age: 54.9 ± 14.4 years). Serum endocan, ET-1, and NT-proBNP were measured by enzyme-linked immunosorbent assay kits. Echocardiography was performed, and carotid-femoral pulse wave velocity (cfPWV) was measured by SphygmoCor in this cross-sectional study. Patients were divided into two groups based on serum endocan median level (cut-off: 44 ug/L). There was significantly higher aorta systolic blood pressure (SBPao) (p = 0.013), NT-proBNP (p = 0.028), albumin/creatinine ratio (p = 0.036), and uric acid (p = 0.045) in the case of the higher endocan group compared to the lower. There was also significantly higher SBPao (p = 0.037) and NT-proBNP (p = 0.038) in the case of higher endothelin-1 (ET-1) levels compared to the lower (cut-off: 231 pg/mL) group by the two-sample t-test. Then, we divided the patients into two groups based on the eGFR (CKD 1-2 vs. CKD 3-5). The levels of serum endocan, NT-proBNP, cfPWV, SBPao, left ventricular mass index (LVMI), uric acid, and albuminuria were significantly higher in the CKD 3-5 group compared to the CKD 1-2 group. The serum endocan and NT-proBNP levels were significantly higher in the diastolic dysfunction group (p = 0.047, p = 0.015). There was a significant increase in serum endocan levels (CKD 1 vs. CKD 5; p = 0.008) with decreasing renal function. In IgAN, vascular biomarkers (endocan, ET-1) may play a role in endothelial dysfunction through vascular damage and elevation of SBPao. Serum endocan, ET-1, and NT-proBNP biomarkers may help to identify IgAN patients at high risk.

IgAN Across the Age Spectrum: The Pediatric Perspective

IgA nephropathy (IgAN) presents with different expressions and natural histories across ages. The direct comparison of incidence and progression of IgAN in children and adults is difficult due to different policies for performing kidney biopsy in different ages and countries. In the past decade the focus has been on assessing the individual risk profile at kidney biopsy or after 1 year of follow-up in children and adults. This would help avoid overtreatment and unnecessary drug exposure in benign cases of IgAN, and promptly initiate an aggressive therapy in progressive ones. This issue is particularly relevant in children. This review addresses some recent insights into the similarities and differences of IgAN across the age spectrum, with a particular focus on the prognostic predictors of progression in children and in adults, aiming at offering some critical elements useful for treatment choices for IgAN across ages.

Clinical Practice Guideline: Microhematuria in Children and Young Adults

BACKGROUND

Occult blood in the urine, or microhematuria, is a common finding (about 10%) in children and young adults. It is often of brief duration and therefore harmless. In persistent microhematuria, acanthocytes in the urine are a frequently unrecognized early marker of glomerular kidney disease. The purpose of this guideline is to promote the early detection of kidney disease in children and young adults with practical, evidence-based recommendations.

METHODS

A systematic search for pertinent publications up to January 2023 was conducted in Pubmed, the Cochrane Database, and Livivo. 474 publications were retrieved, summarized in terms of method and content, and classified by Oxford (2011) evidence level.

RESULTS

Approximately 1% of children and young adults have undiagnosed chronic kidney disease. Microhematuria is an early warning sign. A timely nephrological evaluation is indicated if microhematuria persists for 3 to 6 months, if ≥ 5% acanthocytes are detectable in the urine, and if there is also proteinuria, hypertension, or impaired renal function. Ultrasonography of the kidneys and urinary tract is the imaging method of choice; cystoscopy should be avoided. For patients with glomerular microhematuria, molecular genetic testing is recommended. Renal biopsy is recommended in case of florid glomerular diseases, after the determination of various laboratory param eters and clinical findings, including molecular genet ic testing especially in children.

CONCLUSION

In the absence of a guideline until now, findings have often been incorrectly assessed, leading either to an inadequate work-up or to excessive diagnostics. As a result, in approximately 30% of young patients, valuable opportunities for early treatment to protect the kidneys have been missed.

Weight gain promotes the progression of IgA nephropathy in Asians: A protocol for systematic review and meta-analysis

INTRODUCTION

The relationship between weight gain and progression of IgA nephropathy (IgAN) has been investigated by many researchers but remains controversial. The incidence of IgAN is significantly higher in Asia than in other regions. Therefore, we investigated the relationship between weight gain and primary IgAN in the Asian population.

METHODS AND ANALYSIS

Seven databases were retrieved up to now. We stratified the included population by body mass index (BMI) and performed a meta-analysis of associated risk factors.

OBJECTIVES

In this study, Asian IgAN patients with different BMI were grouped together to clarify the relationship between BMI and IgAN progression in Asian populations, so as to provide more ideas and treatment means for the prevention and treatment of IgAN in the future.

Hyperuricemia: an unrecognized risk factor for kidney-related sequelae in children with hemolytic uremic syndrome

BACKGROUND

Chronic kidney-related sequelae after STEC-HUS occur in 20-40% of patients. Hyperuricemia (HU) may cause acute and chronic toxicity involving the kidneys. We retrospectively assessed if there was an association between the presence of HU during the acute illness and that of kidney-related sequelae in children with STEC-HUS.

METHODS

Children with STEC-HUS who had clinical and laboratory data at 2 years of follow-up were included in this case-control study. Univariate and multivariate analyses were performed between patients with (cases) or without (controls) kidney-related sequelae to identify factors associated with outcomes, including different measures of serum uric acid (sUA) (baseline level, peak, and duration of HU). HU was defined as sUA > 8 mg/dL.

RESULTS

Of 86 patients included, 77.9% had HU. Patients with sequelae (n = 41) had a higher prevalence of HU (41/41 vs. 26/45, p < 0.01), higher baseline leukocyte count, serum creatinine (sCr), and sUA levels as well as lower sodium than controls. During hospitalization, cases also had higher sCr peak, sUA peak and duration of HU, requirement and duration of dialysis, extrarenal complications, and hypertension. By multivariate analysis, after adjusting for length of dialysis, only duration of HU (p = 0.0005; OR 1.7, 95% CI 1.27-2.36) remained as an independent predictor of sequelae, with a best cutoff of 5.5 days (AUC 0.95, specificity 80%, sensitivity 100%).

CONCLUSIONS

The presence of HU is a common finding in children with STEC-HUS and its duration during the acute stage was associated with kidney-related sequelae, regardless of the duration of dialysis. A higher resolution version of the Graphical abstract is available as Supplementary Information.