Application of the International IgA Nephropathy Prediction Tool one or two years post-biopsy

Risk-directed management of chronic kidney disease

The timely and rational institution of therapy is a key step towards reducing the global burden of chronic kidney disease (CKD). CKD is a heterogeneous entity with varied aetiologies and diverse trajectories, which include risk of kidney failure but also cardiovascular events and death. Developments in the past decade include substantial progress in CKD risk prediction, driven in part by the accumulation of electronic health records data. In addition, large randomized clinical trials have demonstrated the effectiveness of sodium-glucose co-transporter 2 inhibitors, glucagon-like peptide 1 receptor agonists and mineralocorticoid receptor antagonists in reducing adverse events in CKD, greatly expanding the options for effective therapy. Alongside angiotensin-converting enzyme inhibitors and angiotensin receptor blockers, these classes of medication have been proposed to be the four pillars of CKD pharmacotherapy. However, all of these drug classes are underutilized, even in individuals at high risk. Leveraging prognostic estimates to guide therapy could help clinicians to prescribe CKD-related therapies to those who are most likely to benefit from their use. Risk-based CKD management thus aligns patient risk and care, allowing the prioritization of absolute benefit in determining therapeutic selection and timing. Here, we discuss CKD prognosis tools, evidence-based management and prognosis-guided therapies.

Population-Level Risk Factors for Kidney Outcomes in IgA Nephropathy: The CURE-CKD Registry

Rationale & Objective

Although IgA nephropathy (IgAN) therapies are advancing quickly, therapeutic interventions are hampered by a lack of kidney disease identification and risk assessment. The study aim was to use population-level data from health systems to identify IgAN and assess risks.

Study Design

A longitudinal and real-world cohort study.

Setting & Participants

Electronic health record data for patients ≥18 years old with IgAN at Providence and University of California Los Angeles health systems during 2016-2022.

Predictors

Health insurance and care utilization along with age, gender, race, ethnicity, estimated glomerular filtration rate (eGFR), urine albumin/creatinine ratio (UACR) or urine protein/creatinine ratio (UPCR), diabetes, hypertension, and medications.

Outcomes

Time to first major adverse kidney event (MAKE): ≥40% eGFR decline; eGFR <15 mL/min/1.73 m2; administrative codes for kidney failure, dialysis, or transplant; and death.

Analytical Approach

Kaplan-Meier survival curves and Cox proportional hazards models.

Results

Patients with IgAN (n = 2,571) were 50% (n = 1,277) women and 58 ± 18 (mean ± SD) years old. At baseline, eGFR was 78 ± 27 mL/min/1.73 m2 (chronic kidney disease epidemiologic 2021 equation); median UACR and UPCR were 166 (interquartile range 25-795) mg/g and 0.7 (0.2-1.8) g/g, respectively, among those with baseline measurements (n = 669). MAKE occurred in 22% of the cohort by 3 years. In Cox proportional hazards models, MAKE was predicted by noncommercial (Medicare or Medicaid) health insurance, hospitalization, more frequent outpatient encounters, lower eGFR, and a higher UACR or UPCR.

Limitations

Missingness, miscoding, and retrospective data.

Conclusions

Substantial loss of kidney function, kidney failure, and death were common events over a short period of time in patients with IgAN. Within health system populations, noncommercial health insurance and greater care utilization augmented risk prediction and could help to identify those who may benefit from closer monitoring and implementation of therapeutic interventions.

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.

Lifetime progression of IgA nephropathy: a retrospective cohort study with extended long-term follow-up

BACKGROUND

IgA nephropathy (IgAN) exhibits an unpredictable trajectory, creating difficulties in prognostication, monitoring, treatment, and research planning. This study provides a comprehensive depiction of the progression of kidney function throughout the disease course, from diagnosis to a span of 36 years post-diagnosis.

METHODS

We utilized a cohort of 400 Norwegian IgAN patients, from diagnosis to the occurrence of death, initiation of kidney replacement therapy (KRT), or the latest follow-up. Recorded proteinuria (n = 2676) and creatinine (n = 8738) measurements were retrieved. Patients were divided into subgroups based on their specific estimated glomerular filtration rate (eGFR) slopes.

RESULTS

Median follow-up was 16 years. During this period, 34% of patients either died or initiated KRT. Among patients who reached endpoint, the median duration from diagnosis to the initiation of KRT or death was 8 years. Notably, 34% of the cohort exhibited a stable disease course, characterized by an eGFR decline of less than 20% between two consecutive measurements. Differences in subsequent disease trajectories among two subgroups with similar eGFR levels at diagnosis could not be accounted for by variations in treatment strategies. Among patients with proteinuria < 1 g/24 h in less than half of the measurements, KRT was five times more prevalent compared to those with more than half of the measurements recording proteinuria < 1 g/24 h (p-value = 0.001).

CONCLUSIONS

While a significant proportion of IgAN patients reach kidney failure within their lifetimes, outcomes vary widely. Clinical data at diagnosis offer limited insights into long-term risks. Enhanced risk stratification necessitates data collection at multiple time points.

Systematic review of the application of the Kidney Failure Risk Equation and Oxford classification in estimating prognosis in IgA Nephropathy

BACKGROUND

IgA nephropathy (IgAN) is the most common primary glomerulonephritis in the world and is an important cause of chronic kidney disease (CKD) and kidney failure. Outcomes are heterogeneous, and accurate risk stratification is important to identify the highest risk individuals for treatment and to help prevent disease progression. The Oxford classification (OC) is an internationally adopted standard for renal biopsy reporting in IgAN, which measures the degree of histological abnormalities and predicts prognosis. The kidney failure risk equation (KFRE) was developed to predict kidney failure in all causes of CKD and has been shown to be highly accurate across diverse etiologies. This review aimed to compare the KFRE with formulae incorporating the OC in accurately determining the risk of kidney failure in IgAN.

METHODS

A systematic review was conducted in accordance with the Cochrane library guidelines and PRISMA statement for reporting of systematic reviews. Studies comparing the accuracy of the KFRE with the OC in predicting disease progression and kidney failure in IgAN were evaluated. The search strategy and analysis were performed independently by two reviewers. Studies that were eligible for inclusion compared the KFRE with any tool incorporating the OC in a cohort of individuals with IgAN. Eligible outcomes were reduction of estimated glomerular filtration rate (eGFR) or end-stage renal disease (ESRD), and prognostic tools were required to assess the accuracy of these formulae by discrimination and/or calibration.

RESULTS

After searching several databases, only one study was eligible for inclusion in the review. This study of 2300 Chinese individuals with IgAN had a median follow-up of 2.5 years. Two-hundred eighty-eight individuals had a composite outcome of 50% decline in eGFR or ESRD, and 214 individuals developed ESRD. Both the KFRE and the IgAN Risk Prediction (IRP) tool (incorporating the OC) were highly accurate at predicting ESRD with a C-statistic of 0.90 and 0.91, respectively. Subgroup analysis demonstrated improved performance of IRP over KFRE in discrimination for individuals with preserved eGFR (> 60 ml/min/1.73 m2) at baseline. The risk of bias was high due to insufficient follow-up and handling of missing data, so overall confidence in findings is very low.

CONCLUSION

There is currently insufficient evidence to compare the accuracy of the KFRE and OC in determining outcomes in IgAN. Further research is required in this field.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42022364569.

Long-term renal survival in patients with IgA nephropathy: a systematic review

The management strategy for IgA nephropathy (IgAN), has undergone constant improvements since the disease entity was first described 50 years ago. However, it is still unknown how these changes affected the long-term renal survival of IgAN patients. We systematically evaluate changes in IgAN renal survival by searching PubMed, Embase, and the Cochrane Library Database of Systematic Reviews from inception to 19 May 2024. We included a large sample of 103076 IgAN cases from 158 studies. Renal survival rates were 94.16% (95% CI: 94.02% to 94.31%), 88.68% (95% CI: 88.48% to 88.87%), and 78.13% (95% CI: 77.82% to 78.43%) at three, five, and ten-year, respectively. Over the past few decades, there haven't been any sound changes in the 3-year and 5-year renal survival rates. The kidney survival rate in developed countries is higher than in developing countries. Researchers consistently show that while proteinuria < 1.0 g/24 h, renal survival rates increase dramatically. In IgAN, long-term renal survival fluctuated rather than continuously improving over time. Our system review's findings indicate that supportive care-the most important recommendation for managing IgAN has shown promising results. The long-term outcomes of IgAN could be significantly improved by the latest developed treatment options.

Emerging perspectives in the management of IgA nephropathy: a comprehensive review

IgA nephropathy (IgAN) is the most prevalent form of primary glomerulonephritis worldwide and a leading cause of chronic kidney disease and renal failure. This disorder is characterized by the deposition of immune complexes containing galactose-deficient forms of IgA and complement C3 in the glomeruli. Until now, disease management relied mainly on optimized supportive care. Systemic corticosteroid therapy is proposed for patients at high risk of disease progression, but the effectiveness and safety of this approach are under debate. A significant proportion of patients do not respond to current therapies and require kidney replacement therapy at a young age, with substantial costs and impact on quality of life. Recently, there have been multiple joint efforts to improve the understanding of IgAN pathophysiology. International collaborations resulted in multiple ongoing clinical trials that are providing new insights toward innovative therapeutic options such as SGLT2 inhibitors, dual endothelin and angiotensin receptor blockers, targeted-release budesonide, B-cell proliferation and differentiation inhibitors, and complement system blockers. Based on this new evidence, revision of the guidelines to manage IgAN is expected to occur in the near future. In addition to the novelty in therapeutic agents, there is also a growing interest in new noninvasive biomarkers for IgAN screening, risk stratification to monitor the course of the disease, and the response to treatment. In this review, we discuss current knowledge on the pathophysiology of IgAN, disease management, and emerging advances in clinical translation of IgAN research.

Application of the updated International IgA Nephropathy Prediction Tool in children one or two years post-biopsy

The pediatric International IgA Nephropathy (IgAN) Prediction Tool comprises two models with and without ethnicity and is the first method to predict the risk of a 30% decline in estimated glomerular filtration rate (eGFR) or kidney failure in children at the time of biopsy using clinical risk factors and Oxford MEST histology scores. However, it is unknown if the Prediction Tool can be applied after a period of observation post-biopsy. Using an international multi-ethnic cohort of 947 children with IgAN, 38% of whom were followed into adulthood, the Prediction Tool was updated for use one year after biopsy. Compared to the original pediatric Prediction Tool, the updated post-biopsy Prediction Tool had a better model fit with higher R2D (51%/50% vs 20%), significant increase in 4-year C-statistics (0.83 vs 0.73/0.69, ΔC 0.09 [95% confidence interval 0.07-0.10] and ΔC 0.14 [0.12-0.15]) and better 4-year calibration with lower integrated calibration indices (0.74/0.54 vs 2.45/1.01). Results were similar after internal validation and when the models were applied two years after biopsy. Trajectories of eGFR after a baseline one year post-biopsy were non-linear and those at higher predicted risk started with a lower eGFR and experienced a more rapid decline over time. In children, eGFR had a variable rate of increase until 15-18 years old and then decreased linearly with a more rapid decline in higher risk groups that was similar to young adults of comparable risk. Thus, the original pediatric Prediction Tool should be used in children at the time of biopsy, and the updated pediatric Prediction Tool should be used to re-evaluate risk one or two years after biopsy.

Representation of multimorbidity and frailty in the development and validation of kidney failure prognostic prediction models: a systematic review

BACKGROUND

Prognostic models that identify individuals with chronic kidney disease (CKD) at greatest risk of developing kidney failure help clinicians to make decisions and deliver precision medicine. It is recognised that people with CKD usually have multiple long-term health conditions (multimorbidity) and often experience frailty. We undertook a systematic review to evaluate the representation and consideration of multimorbidity and frailty within CKD cohorts used to develop and/or validate prognostic models assessing the risk of kidney failure.

METHODS

We identified studies that described derivation, validation or update of kidney failure prognostic models in MEDLINE, CINAHL Plus and the Cochrane Library-CENTRAL. The primary outcome was representation of multimorbidity or frailty. The secondary outcome was predictive accuracy of identified models in relation to presence of multimorbidity or frailty.

RESULTS

Ninety-seven studies reporting 121 different kidney failure prognostic models were identified. Two studies reported prevalence of multimorbidity and a single study reported prevalence of frailty. The rates of specific comorbidities were reported in a greater proportion of studies: 67.0% reported baseline data on diabetes, 54.6% reported hypertension and 39.2% reported cardiovascular disease. No studies included frailty in model development, and only one study considered multimorbidity as a predictor variable. No studies assessed model performance in populations in relation to multimorbidity. A single study assessed associations between frailty and the risks of kidney failure and death.

CONCLUSIONS

There is a paucity of kidney failure risk prediction models that consider the impact of multimorbidity and/or frailty, resulting in a lack of clear evidence-based practice for multimorbid or frail individuals. These knowledge gaps should be explored to help clinicians know whether these models can be used for CKD patients who experience multimorbidity and/or frailty.

SYSTEMATIC REVIEW REGISTRATION

This review has been registered on PROSPERO (CRD42022347295).

An Updated Comprehensive Review on Diseases Associated with Nephrotic Syndromes

There have been exciting advances in our knowledge of primary glomerular diseases and nephrotic syndromes in recent years. Beyond the histological pattern from renal biopsy, more precise phenotyping of the diseases and the use of modern nephrogenetics helps to improve treatment decisions and sometimes also avoid unnecessary exposure to potentially toxic immunosuppression. New biomarkers have led to easier and more accurate diagnoses and more targeted therapeutic decisions. The treatment landscape is becoming wider with a pipeline of promising new therapeutic agents with more sophisticated approaches. This review focuses on all aspects of entities that are associated with nephrotic syndromes with updated information on recent advances in each field. This includes podocytopathies (focal segmental glomerulosclerosis and minimal-change disease), membranous nephropathy, membranoproliferative glomerulonephritis, IgA nephropathy, fibrillary glomerulonephritis, amyloidosis, and monoclonal gammopathy of renal significance in the context of the nephrotic syndrome, but also renal involvement in systemic diseases, diabetic nephropathy, and drugs that are associated with nephrotic syndromes.

The role of complement in kidney disease: conclusions from a Kidney Disease: Improving Global Outcomes (KDIGO) Controversies Conference

Uncontrolled complement activation can cause or contribute to glomerular injury in multiple kidney diseases. Although complement activation plays a causal role in atypical hemolytic uremic syndrome and C3 glomerulopathy, over the past decade, a rapidly accumulating body of evidence has shown a role for complement activation in multiple other kidney diseases, including diabetic nephropathy and several glomerulonephritides. The number of available complement inhibitor therapies has also increased during the same period. In 2022, Kidney Diseases: Improving Global Outcomes (KDIGO) convened a Controversies Conference, "The Role of Complement in Kidney Disease," to address the expanding role of complement dysregulation in the pathophysiology, diagnosis, and management of various glomerular diseases, diabetic nephropathy, and other forms of hemolytic uremic syndrome. Conference participants reviewed the evidence for complement playing a primary causal or secondary role in progression for several disease states and considered how evidence of complement involvement might inform management. Participating patients with various complement-mediated diseases and caregivers described concerns related to life planning, implications surrounding genetic testing, and the need for inclusive implementation of effective novel therapies into clinical practice. The value of biomarkers in monitoring disease course and the role of the glomerular microenvironment in complement response were examined, and key gaps in knowledge and research priorities were identified.

IgA Nephropathy: Epidemiology and Disease Risk Across the World

Despite decades of research, our knowledge of the global epidemiology of IgA nephropathy remains limited. Much of what we know about IgA nephropathy incidence comes from biopsy registry studies that are subject to bias related to differences in screening programs, referral patterns, and access to healthcare. Fewer epidemiologic studies used an appropriate data infrastructure that includes a well-defined source population. Nonetheless, all these studies show considerable geographic variation in disease incidence with an increase from west to east and south to north across Eurasia. This pattern is partly explained by the distribution of genetic risk alleles in individuals of European and East Asian ancestry. Although historically thought to be an indolent disease, recent long-term follow-up studies have demonstrated an exceptionally high lifetime risk of kidney failure. The International IgA Nephropathy Prediction Tool, derived and validated in multiple ethnically diverse cohorts, has improved our ability to identify patients at high risk of progression who may benefit from therapies being tested in clinical trials. The earlier identification of high-risk patients, evaluation of novel risk factors, and accurate assessment of global disease burden require high-quality regional data infrastructures and broad collaborative efforts to ensure the impact of new treatments is maximized.

State-of-Art Therapeutics in IgA Nephropathy

Immunoglobulin-A nephropathy (IgAN) is the most common primary glomerulonephritis in the world, with up to 40% of patients progressing to end-stage kidney disease (ESKD) within 30 years of diagnosis. IgAN is characterized by elevated serum levels of galactose-deficient IgA1 (Gd-IgA1), which leads to immune complex formation and deposition in the glomerular mesangium, causing kidney injury. A diverse disease course and the long-term follow-up required for clinically relevant endpoints (e.g., ESKD) have been barriers to the development of novel therapies in IgAN. Disease management has focused on supportive care with inhibitors of the renin-angiotensin system and, more recently, sodium-glucose transporter inhibitors to control proteinuria. The recent acceptance of proteinuria as a surrogate endpoint by regulatory bodies and a better understanding of disease pathology have helped to initiate the development of several novel treatments. Subsequently, a targeted-release formulation of budesonide and a dual endothelin/angiotensin inhibitor (sparsentan) have received accelerated approval for patients with IgAN. However, additional therapies are needed to target the different pathogenic mechanisms and individualize patient care. Several compounds currently under investigation target various effectors of pathology. There are promising clinical results from emerging compounds that target the generation of Gd-IgA1 by B cells, including inhibitors of A PRoliferation-Inducing Ligand (APRIL) and dual inhibitors of APRIL and B-cell activating factor (BAFF). Other investigational therapies target the complement cascade by inhibiting proteins of the lectin or alternative pathways. As the therapeutic landscape evolves, it will be important to revise treatment guidelines and develop updated standards of care.

Emerging Biochemical and Immunologic Mechanisms in the Pathogenesis of IgA Nephropathy

IgA nephropathy is a mesangioproliferative glomerular disease with significant morbidity and mortality. Most patients with IgA nephropathy develop kidney failure in their lifetime, reducing their life expectancy by a decade. Since its first description in 1968, it has been established that kidneys of IgA nephropathy patients are injured as "innocent bystanders" by nephritogenic IgA1-containing immune complexes. Results from clinical, biochemical, immunologic, and genetic studies suggest a multistep pathogenetic mechanism. In genetically predisposed individuals, this process results in formation of circulating immune complexes due to the binding of IgG/IgA autoantibodies to the polymeric IgA1 molecules with incomplete O-glycosylation. This event is followed by the addition of other proteins, such as complement C3, resulting in the formation of nephritogenic immune complexes. These complexes are not effectively removed from the circulation, and some of them pass through the fenestration of glomerular endothelial cells to enter the mesangial space and activate mesangial cells. It is thought that the process is initiated by soluble immune complexes and that their accumulation results in the formation of immunodeposits that further amplify glomerular injury. Here we summarize current understanding of the pathogenesis of IgA nephropathy and discuss experimental model systems that can inform development of new therapeutic strategies and targets.

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.

Contemporary review of IgA nephropathy

IgA nephropathy (IgAN) is considered the most common primary glomerulonephritis worldwide with a predilection for Asian-Pacific populations and relative rarity in those of African descent. Perhaps 20%-50% of patients progress to kidney failure. The pathogenesis is incompletely understood. Mesangial deposition of immune complexes containing galactose-deficient IgA1 complexed with anti-glycan IgG or IgA antibodies results in mesangial cell activation and proliferation, inflammatory cell recruitment, complement activation, and podocyte damage. Diagnosis requires a biopsy interpreted by the Oxford criteria. Additional pathologic features include podocytopathy, thrombotic microangiopathy, and C4d staining. Biomarkers predicting adverse outcomes include proteinuria, reduced GFR, hypertension, and pathology. Acceptable surrogate endpoints for therapeutic trials include ongoing proteinuria and rate of eGFR decline. The significance of persisting hematuria remains uncertain. The mainstay of therapy is supportive, consisting of lifestyle modifications, renin-angiotensin inhibition (if hypertensive or proteinuric), sodium-glucose-transporter 2 inhibition (if GFR reduced or proteinuric), and endothelin-receptor antagonism (if proteinuric). Immunosuppression should be considered for those at high risk after maximal supportive care. Corticosteroids are controversial with the most positive results observed in Chinese. They carry a high risk of serious side effects. Similarly, mycophenolate may be most effective in Chinese. Other immunosuppressants are of uncertain benefit. Tonsillectomy appears efficacious in Japanese. Active areas of investigation include B-cell inhibition with agents targeting the survival factors BAFF and APRIL and complement inhibition with agents targeting the alternate pathway (Factors B and D), the lectin pathway (MASP-2), and the common pathway (C3 and C5). Hopefully soon, the who and the how of immunosuppression will be clarified, and kidney failure can be forestalled.

Blood and urine biomarkers of disease progression in IgA nephropathy

The prognosis of patients with IgA nephropathy (IgAN) is variable but overall not good. Almost all patients with IgAN are at risk of developing end-stage renal disease within their expected lifetime. The models presently available for prediction of the risk of progression of IgAN, including the International IgA Nephropathy Prediction Tool, consist of traditional clinical, pathological, and therapeutic indicators. Finding biomarkers to improve the existing risk prediction models or replace pathological indicators is important for clinical practice. Many studies have attempted to identify biomarkers for prediction of progression of IgAN, such as galactose-deficient IgA1, complement, a spectrum of protein biomarkers, non-coding RNA, and shedding cells. This article reviews the biomarkers of progression of IgAN identified in recent years, with a focus on those with clinical value, in particular the combination of multiple biomarkers into a biomarker spectrum. Future research should focus on establishing a model based primarily on biomarkers that can predict progression of IgAN and testing it in various patient cohorts.

Machine learning-based diagnosis and prognosis of IgAN: A systematic review and meta-analysis

Purpose

Plenty of studies have explored the diagnosis and prognosis of IgA nephropathy (IgAN) based on machine learning (ML), but the accuracy lacks the support of evidence-based medical evidence. We aim at this problem to guide the precision treatment of IgAN.

Methods

Embase, Pubmed, Cochrane Library, and Web of Science were searched systematically until February 24th, 2024, for publications on ML-based diagnosis and prognosis of IgAN. Subgroup analysis or meta-regression was conducted according to modeling method, follow-up time, endpoint definition, and variable type. Further, the rank sum test was applied to compare the discrimination ability of prognosis.

Results

A total of 47 studies involving 51,935 patients were eligible. Among the 38 diagnostic models, the pooled C-index was 0.902 (95 % CI: 0.878-0.926) in 27 diagnostic models. Of the 162 prognostic models, the C-index for model discrimination of 144 prognostic models was 0.838 (95 % CI: 0.827-0.850) in training. The overall discrimination ability of prognosis was as follows: COX regression > new ML models (e.g. ANN, DT, RF, SVM, XGBoost) > traditional ML models (logistic regression) > Naïve Bayesian network (P < 0.05). External validation of IIgAN-RPT in 19 models showed a pooled C-index of 0.801 (95 % CI: 0.784-0.817).

Conclusions

New ML models have shown application values that are as good as traditional ML models, both in diagnosis and prognosis. In addition, future models are desired to use a more sensitive prognostic endpoint (albuminuria), improve predictive ability in moderate progression risk, and ultimately translate into clinically applicable intelligent tools.

Primary IgA Nephropathy: New Insights and Emerging Therapies

Primary IgA nephropathy (IgAN) is a common glomerular disorder defined by predominant mesangial IgA deposition. Once thought to follow a progressive course in 10-20% of those diagnosed, emerging evidence now suggests most will progress to kidney failure over their lifetimes. Although the lack of safe and effective treatments to impede disease progression continues to present a challenge, the landscape of IgAN has dramatically evolved over the last 2 years. Driven by fundamental changes to accepted end points for IgAN clinical trials as well as fascinating new insights into the pathophysiology of IgAN, a swathe of novel and repurposed therapies are currently being evaluated. Already, two novel drugs, targeted-release formulation budesonide and sparsentan, have received conditional approvals for the treatment of IgAN, with sodium glucose co-transporter 2 inhibitors establishing themselves as further options. Soon to join this ensemble are likely to be treatments that modulate the complement system and B-cell activity; several are currently undergoing clinical trials in IgAN with promising interim results. In this review, we provide an overview of evolving epidemiological insights, disease mechanisms, emerging therapies, and contemporary challenges surrounding the management of IgAN.

Immunoglobulin A glomerulonephropathy: A review

In this editorial, we comment on the article by Meng et al published in the World Journal of Clinical Cases. We comprehensively review immunoglobulin A nephropathy (IgAN), including epidemiology, clinical presentation, diagnosis, and management. IgAN, also known as Berger's disease, is the most frequent type of primary glomerulonephritis (GN) globally. It is mostly found among the Asian population. The presentation can be variable, from microscopic hematuria to a rapidly progressive GN. Around 50% of patients present with single or recurring episodes of gross hematuria. An upper respiratory infection and tonsillitis often precede these episodes. Around 30% of patients present microscopic hematuria with or without proteinuria, usually detected on routine examination. The diagnosis relies on having a renal biopsy for pathology and immunofluorescence microscopy. We focus on risk stratification and management of IgAN. We provide a review of all the landmark studies to date. According to the 2021 KDIGO (kidney disease: Improving Global Outcomes) guidelines, patients with non-variant form IgAN are first treated conservatively for three to six months. This approach consists of adequate blood pressure control, reduction of proteinuria with renin-angiotensin system blockade, treatment of dyslipidemia, and lifestyle modifications (weight loss, exercise, smoking cessation, and dietary sodium restrictions). Following three to six months of conservative therapy, patients are further classified as high or low risk for disease progression. High-risk patients have proteinuria ≥ 1 g/d or < 1 g/d with significant microscopic hematuria and active inflammation on kidney biopsy. Some experts consider proteinuria ≥ 2 g/d to be very high risk. Patients with high and very high-risk profiles are treated with immunosuppressive therapy. A proteinuria level of < 1 g/d and stable/improved renal function indicates a good treatment response for patients on immunosuppressive therapy.

[Immunoglobulin A vasculitis]

The immune-mediated small vessel vasculitis is known as Schoenlein-Henoch purpura predominantly from pediatrics and in these cases occurs more frequently after infections of the upper airways. In adults, immunoglobulin A (IgA) vasculitis often proceeds more severely und recurrently with the classical tetrad of skin manifestations in the sense of leukocytoclastic vasculitis, joint affection, gastrointestinal involvement and IgA nephritis, in contrast to the mostly mild and self-limiting course in children. The background of this systemic vasculitis with formation of IgA immune complexes is considered to be an altered glycosylation of IgA, as this causes the exposure of binding sites for autoantibodies so that an immune complex reaction can be elicited. This ultimately leads to perivascular deposition of IgA and a further activation of neutrophils. Groundbreaking in the diagnostics is the histological detection of leukocytoclastic vasculitis and in cases of renal manifestations a kidney biopsy with characteristic deposits of immune complexes, which cannot be clearly differentiated from IgA nephropathy. The treatment is aimed at the respective manifestation and is mostly based on consensus recommendations due to the lack of randomized studies. In addition to immunosuppressive medication, in the presence of a chronic kidney disease general nephroprotection is becoming increasingly more important also by inhibition of sodium-glucose transporter 2 (SGLT2). The type and extent of kidney involvement and also rare cardiac manifestations are the main determinants of the prognosis. Continuous medical accompaniment of those affected is necessary due to the possible progression of the disease and the risk of recurrence.

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.

Treatment of IgA Nephropathy: A Rapidly Evolving Field

The pivotal event in the pathophysiology of IgA nephropathy is the binding of circulating IgA-containing immune complexes to mesangial cells, with secondary glomerular and tubulointerstitial inflammation and fibrosis. The paramount difficulty in the management of IgA nephropathy is the heterogeneity in its clinical presentation and prognosis, requiring an individualized treatment approach. Goal-directed supportive care remains the bedrock of therapy for all patients, regardless of risk of progression. Sodium-glucose transporter 2 inhibitors and sparsentan should be integral to contemporary supportive care, particularly in patients with chronic kidney damage. Pending the development of reliable biomarkers, it remains a challenge to identify patients prone to progression due to active disease and most likely to derive a net benefit from immunosuppression. The use of clinical parameters, including the degree of proteinuria, the presence of persistent microscopic hematuria, and the rate of eGFR loss, combined with the mesangial hypercellularity, endocapillary hypercellularity, segmental glomerulosclerosis, tubular atrophy/interstitial fibrosis, crescents score, is currently the best approach. Systemic glucocorticoids are indicated in high-risk patients, but the beneficial effects wane after withdrawal and come at the price of substantial treatment-associated toxicity. Therapies with direct effect on disease pathogenesis are increasingly becoming available. While targeted-release budesonide has garnered the most attention, anti-B-cell strategies and selective complement inhibition will most likely prove their added value. We propose a comprehensive approach that tackles the different targets in the pathophysiology of IgA nephropathy according to their relevance in the individual patient.

Machine learning model to estimate probability of remission in patients with idiopathic membranous nephropathy

BACKGROUND

Idiopathic membranous nephropathy (IMN) is a type of nephrotic syndrome and the leading cause of chronic kidney disease. As far as we know, no predictive model for assessing the prognosis of IMN is currently available. This study aims to establish a nomogram to predict remission probability in patients with IMN and assists clinicians to make treatment decisions.

METHODS

A total of 266 patients with histopathology-proven IMN were included in this study. Least absolute shrinkage and selection operator regression was utilized to identify the most important variables. Subsequently, multivariate Cox regression analysis was conducted to construct a nomogram, and bootstrap resampling was employed for internal validation. Receiver operating characteristic and calibration curves and decision curve analysis (DCA) were utilized to assess the performance and clinical utility of the developed model.

RESULTS

A prognostic nomogram was established, which incorporated creatinine, glomerular_basement_membrane_thickening, gender, IgG_deposition, low-density lipoprotein cholesterol, and fibrinogen. The areas under the curves of the 3-, 12-, 24-month were 0.751, 0.725, and 0.830 in the training set, and 0.729, 0.730, and 0.948 in the validation set respectively. These results and calibration curves demonstrated the good discrimination and calibration of the nomogram in the training and validation sets. Additionally, DCA indicated that the nomogram was useful for remission prediction in clinical settings.

CONCLUSION

The nomogram was useful for clinicians to evaluate the prognosis of patients with IMN in early stage.

Understanding patient needs and predicting outcomes in IgA nephropathy using data analytics and artificial intelligence: a narrative review

This narrative review explores two case scenarios related to immunoglobulin A nephropathy (IgAN) and the application of predictive monitoring, big data analysis and artificial intelligence (AI) in improving treatment outcomes. The first scenario discusses how online service providers accurately understand consumer preferences and needs through the use of AI-powered big data analysis. The author, a clinical nephrologist, contemplates the potential application of similar methodologies, including AI, in his medical practice to better understand and meet patient needs. The second scenario presents a case study of a 20-year-old man with IgAN. The patient exhibited recurring symptoms, including gross haematuria and tonsillitis, over a 2-year period. Through histological examination and treatment with renin-angiotensin system blockade and corticosteroids, the patient experienced significant improvement in kidney function and reduced proteinuria over 15 years of follow-up. The case highlights the importance of individualized treatment strategies and the use of predictive tools, such as AI-based predictive models, in assessing treatment response and predicting long-term outcomes in IgAN patients. The article further discusses the collection and analysis of real-world big data, including electronic health records, for studying disease natural history, predicting treatment responses and identifying prognostic biomarkers. Challenges in integrating data from various sources and issues such as missing data and data processing limitations are also addressed. Mathematical models, including logistic regression and Cox regression analysis, are discussed for predicting clinical outcomes and analysing changes in variables over time. Additionally, the application of machine learning algorithms, including AI techniques, in analysing big data and predicting outcomes in IgAN is explored. In conclusion, the article highlights the potential benefits of leveraging AI-powered big data analysis, predictive monitoring and machine learning algorithms to enhance patient care and improve treatment outcomes in IgAN.

Evaluating Progression Risk in Patients With Immunoglobulin A Nephropathy

The highly variable rate of decline in kidney function in patients with immunoglobulin A nephropathy (IgAN) provides a major clinical challenge. Predicting which patients will progress to kidney failure, and how quickly, is difficult. Multiple novel therapies are likely to be approved in the short-term, but clinicians lack the tools to identify patients most likely to benefit from specific treatments at the right time. Noninvasive and validated markers for selecting at-risk patients and longitudinal monitoring are urgently needed. This review summarizes what is known about demographic, clinical, and histopathologic prognostic markers in the clinician's toolkit, including the International IgAN Prediction Tool. We also briefly review what is known on these topics in children and adolescents with IgAN. Although helpful, currently used markers leave clinicians heavily reliant on histologic features from the diagnostic kidney biopsy and standard clinical data to guide treatment choice, and very few noninvasive markers reflect treatment efficacy over time. Novel prognostic and predictive markers are under clinical investigation, with considerable progress being made in markers of complement activation. Other areas of research are the interplay between gut microbiota and galactose-deficient IgA1 expression; microRNAs; imaging; artificial intelligence; and markers of fibrosis. Given the rate of therapeutic advancement, the remaining gaps in biomarker research need to be addressed. We finish by describing our route to clinical utility of predictive and prognostic markers in IgAN. This route will provide us with the chance to improve IgAN prognosis by using robust, clinically practical markers to inform patient care.

Dynamics of urine proteomics biomarker and disease progression in patients with IgA nephropathy

BACKGROUND

Immunoglobulin A nephropathy (IgAN) frequently leads to kidney failure. The urinary proteomics-based classifier IgAN237 may predict disease progression at the time of kidney biopsy. We studied whether IgAN237 also predicts progression later in the course of IgAN.

METHODS

Urine from patients with biopsy-proven IgAN was analyzed using capillary electrophoresis-mass spectrometry at baseline (IgAN237-1, n = 103) and at follow-up (IgAN237-2, n = 89). Patients were categorized as "non-progressors" (IgAN237 ≤0.38) and "progressors" (IgAN237 >0.38). Estimated glomerular filtration rate (eGFR) and urinary albumin-creatinine ratio slopes were calculated.

RESULTS

Median age at biopsy was 44 years, interval between biopsy and IgAN237-1 was 65 months and interval between IgAN237-1 and IgAN237-2 was 258 days (interquartile range 71-531). IgAN237-1 and IgAN237-2 values did not differ significantly and were correlated (rho = 0.44, P < .001). Twenty-eight percent and 26% of patients were progressors based on IgAN237-1 and IgAN237-2, respectively. IgAN237 inversely correlated with chronic eGFR slopes (rho = -0.278, P = .02 for score-1; rho = -0.409, P = .002 for score-2) and with ±180 days eGFR slopes (rho = -0.31, P = .009 and rho = -0.439, P = .001, respectively). The ±180 days eGFR slopes were worse for progressors than for non-progressors (median -5.98 versus -1.22 mL/min/1.73 m2 per year for IgAN237-1, P < .001; -3.02 vs 1.08 mL/min/1.73 m2 per year for IgAN237-2, P = .0047). In multiple regression analysis baseline progressor/non-progressor according to IgAN237 was an independent predictor of eGFR180days-slope (P = .001).

CONCLUSION

The urinary IgAN237 classifier represents a risk stratification tool in IgAN also later in the course of the dynamic disease. It may guide patient management in an individualized manner.

IgA nephropathy

IgA nephropathy (IgAN), the most prevalent primary glomerulonephritis worldwide, carries a considerable lifetime risk of kidney failure. Clinical manifestations of IgAN vary from asymptomatic with microscopic or intermittent macroscopic haematuria and stable kidney function to rapidly progressive glomerulonephritis. IgAN has been proposed to develop through a 'four-hit' process, commencing with overproduction and increased systemic presence of poorly O-glycosylated galactose-deficient IgA1 (Gd-IgA1), followed by recognition of Gd-IgA1 by antiglycan autoantibodies, aggregation of Gd-IgA1 and formation of polymeric IgA1 immune complexes and, lastly, deposition of these immune complexes in the glomerular mesangium, leading to kidney inflammation and scarring. IgAN can only be diagnosed by kidney biopsy. Extensive, optimized supportive care is the mainstay of therapy for patients with IgAN. For those at high risk of disease progression, the 2021 KDIGO Clinical Practice Guideline suggests considering a 6-month course of systemic corticosteroid therapy; however, the efficacy of systemic steroid treatment is under debate and serious adverse effects are common. Advances in understanding the pathophysiology of IgAN have led to clinical trials of novel targeted therapies with acceptable safety profiles, including SGLT2 inhibitors, endothelin receptor blockers, targeted-release budesonide, B cell proliferation and differentiation inhibitors, as well as blockade of complement components.

IgA nephropathy in adults-treatment standard

Immunoglobulin A nephropathy (IgAN) is the most common primary form of glomerular disease worldwide and carries a high lifetime risk of kidney failure. The underlying pathogenesis of IgAN has been characterized to a sub-molecular level; immune complexes containing specific O-glycoforms of IgA1 are central. Kidney biopsy remains the gold-standard diagnostic test for IgAN and histological features (i.e. MEST-C score) have also been shown to independently predict outcome. Proteinuria and blood pressure are the main modifiable risk factors for disease progression. No IgAN-specific biomarker has yet been validated for diagnosis, prognosis or tracking response to therapy. There has been a recent resurgence of investigation into IgAN treatments. Optimized supportive care with lifestyle interventions and non-immunomodulatory drugs remains the backbone of IgAN management. The menu of available reno-protective medications is rapidly expanding beyond blockade of the renin-angiotensin-aldosterone system to include sodium-glucose cotransporter 2 and endothelin type A receptor antagonism. Systemic immunosuppression can further improve kidney outcomes, although recent randomized controlled trials have raised concerns regarding infectious and metabolic toxicity from systemic corticosteroids. Studies evaluating more refined approaches to immunomodulation in IgAN are ongoing: drugs targeting the mucosal immune compartment, B-cell promoting cytokines and the complement cascade are particularly promising. We review the current standards of treatment and discuss novel developments in pathophysiology, diagnosis, outcome prediction and management of IgAN.

Novel agents for treating IgA nephropathy

PURPOSE OF REVIEW

In the past, the treatment of IgA nephropathy (IgAN), which is the most common glomerulonephritis worldwide, mostly relied on blockade of the renin-angiotensin system as a central component of so-called supportive therapy as well as on high-dose systemic corticosteroid therapy.

RECENT FINDINGS

The supportive treatment arm has been expanded by the addition of sodium-glucose cotransporter-2 inhibitors, hydroxychloroquine, and, most recently, endothelin A receptor blockers. Treatment with high-dose systemic corticosteroids has become more controversial, with some studies observing no benefit and others documenting the protection of kidney function. However, all recent studies on systemic corticosteroids consistently found significant toxicity. An important novel approach to IgAN, therefore, is therapy with a targeted release formulation of budesonide with preferential release in the distal small intestine, given the mounting evidence for a gut-kidney axis in the pathophysiology of IgAN. In addition, emerging new therapeutic options include a variety of complement inhibitors as well as agents targeting B-cell proliferation and differentiation.

SUMMARY

In recent years, IgAN has become the focus of a considerable number of clinical studies that will significantly advance the development of new therapy strategies.

Systematic Review of the Oxford Classification of IgA Nephropathy: Reproducibility and Prognostic Value

Key Points

The Oxford classification of IgA nephropathy defined five features scored subjectively in renal biopsies, identified by the initials MESTC. Two large studies with independent observers showed reproducibility was moderate for T, moderate or poor for M and S, and poor for E and C. In multivariate analyses including clinical features, T was related to 58% of outcomes, with no correlation of MESTC with 24% of outcomes.

Background

The Oxford classification of IgA nephropathy defined five prognostic features scored subjectively in renal biopsies: mesangial cellularity (M), endocapillary hypercellularity (E), segmental sclerosis (S), interstitial fibrosis/tubular atrophy (T), and (fibro)cellular crescents (C). Pathological scoring systems should be reproducible and have prognostic value independently of clinical features. Reproducibility of the classification was not previously investigated in a systematic review, and the most recent systematic reviews of prognostic value were in 2017.

Methods

This systematic review followed PRISMA 2020 guidelines. MEDLINE, PUBMED, and EMBASE databases were searched using the terms “IgA nephropathy” and “Oxford.” Eligible papers applied the classification and mentioned statistical analysis of interobserver reproducibility and/or included multivariate analysis of outcomes related to individual Oxford scores and clinical features, including treatment with corticosteroids or other immunosuppressive drugs.

Results

There were 99 suitable papers before September 23, 2022. Of 12 papers that mentioned reproducibility, only six reported statistics for MEST/MESTC scoring. Four of these were small studies and/or had observers at the same institution. These were considered less representative of application of the classification than two large studies with independent observers, in which agreement was moderate for T, either moderate or poor for M and S, and poor for E and C. In 92 papers with 125 multivariate analyses of various outcomes, the commonest Oxford element associated with outcomes was T (73 of 125, 58%), with no correlation of any element with outcomes in 30 analyses (24%). Treatment with immunosuppression was often related to scores, particularly C and E, without consistent relations between Oxford scores and outcomes in immunosuppressed patients.

Conclusions

This systematic review showed limitations of the Oxford classification in practice, particularly the moderate or poor reproducibility of scores. T was the Oxford score most often related to clinical outcomes, but even this was not consistently reliable as a prognostic indicator.

KDOQI US Commentary on the 2021 KDIGO Clinical Practice Guideline for the Management of Glomerular Diseases

The KDIGO 2021 Clinical Practice Guideline for the Management of Glomerular Diseases represents the first update to this set of recommendations since the initial set of KDIGO guideline recommendations was published in 2012. The pace of growth in our molecular understanding of glomerular disease has quickened and a number of newer immunosuppressive and targeted therapies have been introduced since the original set of guideline recommendations, making such an update necessary. Despite these updates, many areas of controversy remain. In addition, further updates since the publication of KDIGO 2021 have occurred which this guideline does not encompass. With this commentary, the KDOQI work group has generated a chapter-by-chapter companion opinion article that provides commentary specific to the implementation of the KDIGO 2021 guideline in the United States.

A bibliometric analysis of complement in IgA nephropathy from 1991 to 2022

Introduction: IgA nephropathy is a common glomerular disease on a global scale, which has resulted in significant economic burdens. The complement system plays a vital role in enhancing the efficacy of antibodies and phagocytic cells in eliminating microbes and damaged cells, and promoting inflammation. Complement activation has been found to contribute to the progression of various renal diseases, including IgA nephropathy. Methods: In this study, a thorough analysis was conducted on publications related to complement in IgAN from 1991 to 2022, retrieved from the Web of Science Core Collection and Scopus database. The analysis focused on various aspects such as annual publications, country, institution, author, journal, keywords, and co-cited references, utilizing Citespace and Vosviewer. Results: A total of 819 publications were obtained, and while there were slight fluctuations in annual publications, an overall upward trend was observed. China, Japan and the United States were the leading countries in terms of publications, with China having the highest number of publications (201). Collaborative network analysis revealed that England, University of Alabama Birmingham, and Robert J Wyatt were the most influential country, institution, and author, respectively, in this field of research. Furthermore, the analysis of references and keywords indicated that complement activation contributes to IgAN, and immunosuppression in IgAN are a hot topic of research. Discussion: This study identifies current research hotspots and advanced tendencies in the study of complement in IgAN, providing scholars with crucial directions in this research area.

An update on corticosteroid treatment for IgA nephropathy

PURPOSE OF REVIEW

The use of corticosteroids to treat IgA nephropathy (IgAN) has been limited by many controversies related to uncertain benefit and safety concerns. Recent trials have tried to address these limitations.

RECENT FINDINGS

After being paused because of an excess of adverse events in the full-dose steroid arm, the TESTING trial compared a reduced dose of methylprednisolone to placebo in patients with IgAN after optimization of supportive therapy. Steroid treatment was associated with a significant reduction in the risk of a 40% decline in estimated glomerular filtration rate (eGFR), kidney failure and kidney death as well as a sustained decrease in proteinuria compared with placebo. Serious adverse events were more frequent with the full dose regimen but less common in the reduced dose regimen. A phase III trial evaluating a new formulation of targeted-release budesonide showed a significant reduction in short-term proteinuria and has resulted in accelerated FDA approval for use in the United States. In a subgroup analysis of DAPA-CKD trial, sodium-glucose transport protein 2 inhibitors reduced the risk of kidney function decline in patients who have completed or are not eligible for immunosuppression.

SUMMARY

Both reduced-dose corticosteroids and targeted-release budesonide are new therapeutic options that can be used in patients with high-risk disease. More novel-targeted therapies with a better safety profile are currently under investigations.

Use of Histologic Parameters to Predict Glomerular Disease Progression: Findings From the China Kidney Biopsy Cohort Study

RATIONALE & OBJECTIVE

Challenges in achieving valid risk prediction and stratification impede treatment decisions and clinical research design for patients with glomerular diseases. This study evaluated whether chronic histologic changes, when complementing other clinical data, improved the prediction of disease outcomes across a diverse group of glomerular diseases.

STUDY DESIGN

Multicenter retrospective cohort study.

SETTING & PARTICIPANTS

4,982 patients with biopsy-proven glomerular disease who underwent native biopsy at 8 tertiary care hospitals across China in 2004-2020.

NEW PREDICTORS & ESTABLISHED PREDICTORS

Chronicity scores depicted as 4 categories of histological chronic change, as well as baseline clinical and demographic variables.

OUTCOME

Progression of glomerular disease defined as a composite of kidney failure or a ≥40% decrease in estimated glomerular filtration rate from the measurement at the time of biopsy.

ANALYTICAL APPROACH

Multivariable Cox proportional hazard models. The performance of predictive models was evaluated by C statistic, time-dependent area under the receiver operating characteristic curve (AUROC), net reclassification index, integrated discrimination index, and calibration plots.

RESULTS

The derivation and validation cohorts included 3,488 and 1,494 patients, respectively. During a median of 31 months of follow-up, a total of 444 (8.9%) patients had disease progression in the 2 cohorts. For prediction of the 2-year risk of disease progression, the AUROC of the model combining chronicity score and the Kidney Failure Risk Equation (KFRE) in the validation cohort was 0.76 (95% CI, 0.65-0.87); in comparison with the KFRE model (AUROC, 0.68 [95% CI, 0.56-0.79]), the combined model was significantly better (P = 0.04). The combined model also had a better fit, with a lower Akaike information criterion and a significant improvement in reclassification as assessed by the integrated discrimination improvements and net reclassification improvements. Similar improvements in predictive performance were observed in subgroup and sensitivity analyses.

LIMITATIONS

Selection bias, relatively short follow-up, lack of external validation.

CONCLUSIONS

Adding histologic chronicity scores to the KFRE model improved the prediction of kidney disease progression at the time of kidney biopsy in patients with glomerular diseases.

PLAIN-LANGUAGE SUMMARY

Risk prediction and stratification remain big challenges for treatment decisions and clinical research design for patients with glomerular diseases. The extent of chronic changes is an important component of kidney biopsy evaluations in glomerular disease. In this large multicenter cohort including 4,982 Chinese adults undergoing native kidney biopsy, we evaluated whether histologic chronicity scores, when added to clinical data, could improve the prediction of disease prognosis for a diverse set of glomerular diseases. We observed that adding histologic chronicity scores to the kidney failure risk equation improved the prediction of kidney disease progression at the time of kidney biopsy in patients with glomerular diseases.

A Primer in Precision Nephrology: Optimizing Outcomes in Kidney Health and Disease through Data-Driven Medicine

This year marks the 63rd anniversary of the International Society of Nephrology, which signaled nephrology's emergence as a modern medical discipline. In this article, we briefly trace the course of nephrology's history to show a clear arc in its evolution-of increasing resolution in nephrological data-an arc that is converging with computational capabilities to enable precision nephrology. In general, precision medicine refers to tailoring treatment to the individual characteristics of patients. For an operational definition, this tailoring takes the form of an optimization, in which treatments are selected to maximize a patient's expected health with respect to all available data. Because modern health data are large and high resolution, this optimization process requires computational intervention, and it must be tuned to the contours of specific medical disciplines. An advantage of this operational definition for precision medicine is that it allows us to better understand what precision medicine means in the context of a specific medical discipline. The goal of this article was to demonstrate how to instantiate this definition of precision medicine for the field of nephrology. Correspondingly, the goal of precision nephrology was to answer two related questions: ( 1 ) How do we optimize kidney health with respect to all available data? and ( 2 ) How do we optimize general health with respect to kidney data?

IgA Nephropathy: Current Understanding and Perspectives on Pathogenesis and Targeted Treatment

Immunoglobulin A nephropathy (IgAN) is the most common primary glomerulonephritis worldwide, with varied clinical and histopathological features between individuals, particularly across races. As an autoimmune disease, IgAN arises from consequences of increased circulating levels of galactose-deficient IgA1 and mesangial deposition of IgA-containing immune complexes, which are recognized as key events in the widely accepted "multi-hit" pathogenesis of IgAN. The emerging evidence further provides insights into the role of genes, environment, mucosal immunity and complement system. These developments are paralleled by the increasing availability of diagnostic tools, potential biomarkers and therapeutic agents. In this review, we summarize current evidence and outline novel findings in the prognosis, clinical trials and translational research from the updated perspectives of IgAN pathogenesis.

Assessing prognosis in IgA nephropathy

Assessing the prognosis is essential in chronic diseases, such as IgA nephropathy. The 2021 Kidney Disease: Improving Global Outcomes (KDIGO) guidelines recommend the "International IgAN Prediction Tool" (available at www.qxmd.com) for this. The key limitation was that the tool was only validated at the time of the kidney biopsy. An improved algorithm is now described, which allows assessing the prognosis at 1 or 2 years after biopsy. Herein, we review the strengths, limitations, and potential clinical usefulness of this new prediction tool.

Crescents and IgA Nephropathy: A Delicate Marriage

IgA nephropathy (IgAN) is a progressive disease with great variability in the clinical course. Among the clinical and pathologic features contributing to variable outcomes, the presence of crescents has attracted particular interest as a distinct pathological feature associated with severity. Several uncontrolled observations have led to the general thought that the presence and extent of crescents was a prognostic indicator associated with poor outcomes. However, KDIGO 2021 guidelines concluded that either the presence or the relative number of crescents should not be used to determine the progression of IgAN nor should they suggest the choice of immunosuppression. Our aim is to report and discuss recent data on the debated issue of the value of active (cellular and fibrocellular) crescents in the pathogenesis and clinical progression of IgAN, their predictive value, and the impact of immunosuppression on renal function. We conclude that the value of crescents should not be disregarded, although this feature does not have an independent predictive value for progression in IgAN, particularly when considering immunosuppressed patients. An integrated overall evaluation of crescents with other active MEST scores, clinical data, and novel biomarkers must be considered in achieving a personalized therapeutic approach to IgAN patients.