IgA Nephropathy in Native Kidneys: Oxford and Banff Classifications Reveal Distinct Profiles and Predict Outcomes in Pediatric and Adult Patients

IgA nephropathy is the most common primary glomerulonephritis, with pathohistological changes described by the Oxford classification, while the Banff classification is used in transplant pathology. This study included 253 patients with IgA nephropathy in native kidneys, divided into the pediatric (<i>n</i> = 105) and adult (<i>n</i> = 148) groups. It aimed to examine clinical, and Oxford and Banff morphological parameters in relation to age, correlations of clinical data with pathohistological parameters, and predictors of the disease outcome. Pediatric patients more frequently presented with macroscopic hematuria, while adults showed higher urea and creatinine levels, and lower eGFR. Examining Oxford classification parameters, chronic glomerular and tubulointerstitial lesions were more common in adults. Banff parameters revealed more frequent chronically active glomerular, inflammatory, chronic tubulointerstitial, and vascular lesions in adults. All inflammatory, chronic tubulointerstitial, and vascular parameters correlated with serum urea levels, eGFR and CKD stage in adults, while less frequent in pediatric patients. Tubulointerstitial Oxford and Banff parameters were strong predictors of CKD and proteinuria progression in children, while such predictors were fewer in adults; segmental glomerulosclerosis predicted hematuria progression in adults. Banff parameters (cg, t, ti, i, i-IFTA, ptc, cv), not in Oxford classification, significantly predict outcomes and are recommended for incorporation into IgA nephropathy reports.