External validation of the international immunoglobulin A nephropathy (IgAN) prediction tool in Korean children with IgAN.

Background: The International IgA nephropathy (IgAN) Prediction Tool was recently updated to predict the risk of a 30% decline in estimated glomerular filtration rate (eGFR) or kidney failure in children with IgAN. We aimed to evaluate the clinical performance of this tool in a Korean cohort of children with IgAN.

Methods: We calculated the predicted risk for biopsy-proven IgAN children from 20 Korean centers. The primary outcome was a 30% decline in eGFR or kidney failure. Discrimination and calibration performances of two pre-developed models were first evaluated. Subsequently, we constructed an updated model for Korean children using clinically meaningful variables.

Results: The study included 472 children with a mean age of 11.4 years. During a median follow-up period of 47.5 months, 58 patients (14.0%) reached the primary outcome. The two prediction models from the International IgA Nephropathy Prediction Tool exhibited suboptimal prediction power, with an integrated area under the curve (AUC) level of 0.57 (model with race) and 0.55 (model without race), respectively. The updated model, incorporating additional coefficients (sex, body mass index, serum albumin, presenting symptoms), showed good agreement between predicted risk and observed outcomes for Korean children (integrated AUC level of 0.70), significantly better than the IgAN International tool. Various model performance assessments showed consistent results. External validation with 145 children also demonstrated a superior fit for our model.

Conclusion: The updated International IgA Nephropathy Prediction Tool for children had suboptimal prediction ability in Korean IgAN children whereas our proposed model showed acceptable prediction ability in this population.