IgAN.pt: External Validation of the International IgA Nephropathy Prediction Tool in a Portuguese Cohort

Abstract Introduction: IgA nephropathy (IgAN) is one of the most common primary glomerulonephritis worldwide, presenting with highly variable clinical manifestations and disease progression. The 10‑year risk of end‑stage kidney disease (ESKD) ranges from 5% to 60%, making risk stratification a major challenge. To address this, the IgAN‑Prediction Tool (IgAN‑PT) was developed and is currently recommended for risk assessment. Methods: This study aimed to evaluate the applicability of the IgAN-PT in a Portuguese cohort. We conducted a retrospective analysis of all biopsy‑confirmed IgAN cases from January 1998 to December 2018 and assessed the tool’s predictive performance. Results: In a cohort of 93 Portuguese patients, the IgAN‑PT significantly correlated with 5‑year progression to ESKD or a ≥50% reduction in eGFR (OR 1.06; 95%CI [1.02‑1.1]), demonstrating good discriminative performance (AUC 0.75; 95%CI [0.681‑0.910]). Additionally, baseline proteinuria >1.4 g/24h, eGFR <79 mL/min/1.73m², and an IgAN‑PT score >12.4% provided the best sensitivity‑specificity compromise for predicting the primary outcome. A multivariate model incorporating both IgAN‑PT and the presence of crescents showed improved predictive capacity compared with IgAN‑PT alone (AUC 0.845; 95%CI [0.754‑0.937]). Conclusion: Our findings validate the use of IgAN‑PT in a Portuguese cohort and suggest that incorporating the presence of crescents enhances its predictive accuracy.