ABSTRACT Aim To externally validate the International IgA Nephropathy Prediction Tool (IIgANN‐PT) in a Colombian Hispanic cohort with biopsy‐proven IgA nephropathy (IgAN). Methods We conducted a retrospective cohort study of 397 Colombian Hispanic adults with primary IgAN biopsied between 2004 and 2022 and followed through 1 April 2024. The race‐unadjusted IIgANN‐PT was applied at biopsy to predict the composite outcome of sustained 50% decline in estimated glomerular filtration rate (eGFR) or end‐stage kidney disease (ESKD). Model performance was evaluated at the pre‐specified 5‐year horizon using time‐dependent AUC and Harrell's C‐statistic for discrimination, inverse‐probability‐of‐censoring‐weighted (IPCW) Brier score for overall prediction error and calibration‐in‐the‐large (CITL) plus calibration slope (βLP) for calibration. Predicted and observed 5‐year risks were also compared across the tool's four pre‐specified linear predictor risk strata. Results Over a median follow‐up of 4.7 years, 132/397 (33.3%) patients reached the composite outcome. In the complete‐case analysis ( n = 234), discrimination at 5 years was excellent (AUC 0.94 95% CI 0.89–0.97; Harrell's C 0.88), with low overall prediction error (IPCW Brier score 0.103). Calibration was accurate on average (CITL 0.03), but the calibration slope was > 1 (βLP 1.40), indicating underprediction concentrated at the extremes; the largest underestimation occurred in the very‐high‐risk stratum (mean predicted ~67% vs. observed ~80%–85%). Conclusion In this Colombian Hispanic IgAN cohort, the IIgANN‐PT retained excellent 5‐year discrimination and good average calibration, but underestimated risk in the highest‐risk patients, supporting its use for risk stratification while emphasising the need for calibration assessment (and potential local recalibration) before broader implementation.
Rodelo‐Ceballos et al. (Sun,) studied this question.