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External validation of the pediatric International IgA Nephropathy Prediction Tool in a central China cohort
Daojing Ying1, Mengke Lu1, Yuanzhao Zhi1
1Department of Pediatrics, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, People's Republic of China.
Insights
The pediatric International IgA Nephropathy (IgAN) Prediction Tool needs improvement. While the model without race identified highest-risk patients, overall discrimination and calibration were unsatisfactory for predicting kidney disease progression in children.
Area of Science:
- Nephrology
- Pediatric Nephrology
- Clinical Epidemiology
Background:
- The International IgA Nephropathy (IgAN) Prediction Tool, adapted from adult data, requires external validation in pediatric populations.
- Idiopathic IgA Nephropathy (IgAN) is a significant cause of chronic kidney disease in children.
Purpose of the Study:
- To externally validate the updated pediatric International IgA Nephropathy (IgAN) Prediction Tool.
- To assess the tool's ability to predict kidney disease progression in a contemporary cohort of children with IgAN.
Main Methods:
- External validation of the IgAN Prediction Tool in 439 children with biopsy-confirmed idiopathic IgAN.
- Primary outcome: 30% decline in estimated glomerular filtration rate (eGFR) or end-stage kidney disease.
- Evaluation of discrimination (C-index, ROC curve) and calibration (calibration plots) for models with and without race.
Main Results:
- The cohort had milder proteinuria and lower IgAN lesion severity compared to previously reported studies.
- Discrimination (C-index, AUC) was below 0.7 at 5 years for both models, indicating poor predictive performance.
- Both models generally overestimated the risk of kidney disease progression, with unsatisfactory calibration.
Conclusions:
- The IgAN Prediction Tool, even without race adjustment, showed limited ability to accurately stratify risk in this pediatric cohort.
- The model without race demonstrated some ability to distinguish the highest-risk group but overall performance was unsatisfactory.
- External validation revealed suboptimal discrimination and calibration, suggesting the need for further refinement of prediction tools for pediatric IgAN.
Background:
This study aimed to externally validate the pediatric International IgA Nephropathy (IgAN) Prediction Tool updated from the adult IgAN Prediction Tool.
Methods:
439 children with biopsy-confirmed idiopathic IgAN were enrolled in this external validation study. The primary outcome was a 30% decline in eGFR or end-stage kidney disease. We evaluated the discrimination using Harrell's C-index, the receiver operating characteristic (ROC) curve, and Kaplan-Meier curves for four risk groups (< 16th [low risk], ∼16 to < 50th [intermediate risk], ∼50 to < 84th [high risk], and ≥ 84th percentiles [highest risk] of linear predictor). Calibration was assessed using calibration plots.
Results:
The median follow-up time of the 439 patients was 4.5 (2.7-6.8) years, and 27 patients reached the primary outcome. Compared with the reported cohorts, our cohort was more contemporary, with milder proteinuria at biopsy, and had lower proportions of S1 and T1 lesions. Harrell's C-index and area under the ROC curve at 5 years were < 0.7 for both the models with and without race. The Kaplan-Meier curves of the risk groups were not well separated for the two models, only separated completely between the highest-risk group and the others for the model without race. The two models generally overestimated the risk of the primary outcome, CONCLUSION: The model without race could accurately distinguish the highest-risk patients from patients with low, intermediate, and high risk for kidney progression. Discrimination and calibration for the full model with or without race were unsatisfactory in this contemporary cohort in central China.
