LAUSR

IgA nephropathy (IgAN) is the most common primary glomerulopathy worldwide, with 20%–40% of patients developing chronic kidney disease (CKD) within 10–20 years of diagnosis. There is great variability in the clinical course of IgAN. Proteinuria >1 g/day is the strongest predictor of disease progression. The International IgAN Prediction Tool (IgAN PT) estimates the risk of a 50% decline in the estimated glomerular filtration rate (eGFR) or progression to CKD. While it has been validated in Asian, European, and North American populations, its accuracy in Latin American populations remains unknown. There is insufficient evidence to guide treatment decisions on the basis of the IgAN PT, persistent microscopic hematuria, or Oxford classification. The primary objective of this study is to present an overview of the clinical and histopathological characteristics at the time of diagnosis within a Mexican cohort of patients with IgAN, and to assess the performance of the IgAN PT in this population. Observational and retrospective cohort study at a third level center from 1992 to 2024. Records of 46 patients with histopathological diagnoses of IgAN were obtained and 12 were excluded because of a lack of follow-up data. The score of the IgAN PT was calculated and follow-up was performed after 24 months of the biopsy. Clinical and histopathological characteristics are presented as median (interquartile range) or mean (standard deviation), and absolute frequency (percentage) according to the variable type and its distribution. The receiver operating characteristic (ROC) curve was used to assess the diagnostic performance of the IgAN PT in this population. The area under the curve (AUC) values were as follows: AUC ≥ 0.9 excellent; 0.8 ≤ AUC < 0.9 considerable and 0.7 ≤ AUC < 0.8 fair. Thirty-three patients were included (Table 1), 54.5% were female, with a median age of 39.2 years and an average body mass index of 26.6 Kg/m². Only 27.2% had a prior infection, and 18.2% had a history of preeclampsia. The most common clinical presentations included rash, edema, and hematuria. Hematuria-proteinuria syndrome was observed in 57.6% of the patients. At the time of biopsy, the mean estimated glomerular filtration rate (eGFR) was 48.2 mL/min/1.73 m², and the proteinuria/creatinuria ratio (PCR) was 1.8 g/g. Notably, 45.4% of patients had antinuclear antibodies titres >1:40, while only 12.1% had decreased C3 levels, with no reduction in C4 levels. Renal biopsy revealed mesangial hypercellularity (M1) in 93.9%, and segmental sclerosis (S1) in 87.9% of the cases. Immunofluorescence analysis showed 3-4+ IgA deposits in 78% of patients, with C3 in 78.7% of cases. At two years of follow-up, 10 patients (30.3%) developed CKD, 5 patients (15.2%) experienced a 50% decline in eGFR, and 4 (12.12%) patients required renal replacement therapy. Regarding proteinuria, 25 patients (80.6%) achieved a 50% reduction in the PCR, and 23 patients (74.2%) reduced their PCR to <0.5 g/g. ROC analysis showed excellent discriminatory abilities with an AUC value of 0.95 for predicting 50% decline in eGFR and considerable discriminatory abilities with an AUC value of 0.870 for predicting CKD (Fig. 1). IgAN PT performs well in the Mexican population and clinicians can use it to predict the risk of a 50% decline in eGFR from baseline and use it with discretion for progression to CKD.