The relationship between histological variants, treatment, and renal outcome of IgA nephropathy: A single-center experience

Immunoglobulin A nephropathy (IgAN) is the most common primary glomerulonephritis. The 2016 Oxford mesangial hypercellularity, endocapillary hypercellularity, segmental glomerular sclerosis, tubular atrophy (T), cellular crescent classification is essential for early prognosis and treatment guidance, which may include supportive care and glucocorticoids. Although research on IgAN is advancing, the links between early findings and long-term kidney outcomes remain unclear. This study aims to clarify relationships among histological variants, treatment, and long-term renal changes. We conducted a single-center, retrospective cohort study, collecting and analyzing baseline characteristics, treatments, and histopathological data. Clinical data, including serum creatinine (sCr), reciprocal of sCr (1/sCr), blood urea nitrogen, urinary protein-to-creatinine ratio, and total protein-to-creatinine ratio (TPCR), were gathered before renal biopsy and during follow-up. Renal endpoints were defined as estimated glomerular filtration rate < 30 mL/min/1.73 m ² and ≥ 50% decline in estimated glomerular filtration rate at follow-up. Kaplan–Meier analyses and Cox proportional hazards models were employed. Thirty-eight patients were included in the study, with a median follow-up period of 36 months. The Kaplan–Meier analyses revealed no significant differences in outcomes based on immunosuppressive therapy or the Oxford T score for endpoints A or D. However, the baseline TPCR tertiles displayed a consistent trend-level separation. Regarding the mesangial hypercellularity, endocapillary hypercellularity, segmental glomerular sclerosis, T, cellular crescent scores, we found that the extent of tubular atrophy was a significant negative predictor for changes in sCr ( P  = .017), the reciprocal of sCr (1/sCr) ( P  < .001), and blood urea nitrogen ( P  = .029). In multivariable Cox models, baseline TPCR independently predicted both endpoint A (hazard ratio 2.71, 95% confidence intervals 1.02–7.20) and endpoint D (hazard ratio 7.56, 95% confidence intervals 1.54–37.17). While the Oxford T score did not have an independent association with time-to-event outcomes, it was strongly correlated with continuous renal function parameters. Immunosuppressive therapy, such as corticosteroids, did not significantly enhance long-term renal function or urinary protein levels in our relatively small cohort. However, we found that tubular atrophy, indicated by the T score, had a significant negative predictive value for changes in renal parameters. Based on the T score, a repeat renal biopsy may be useful to evaluate the extent of kidney damage and the prognosis of IgAN.