Background: Although more than 40 years have passed since IgA nephropathy (IgAN) was first reported, predicting the renal outcome of individual IgAN patients remains difficult. Emerging epidemiologic evidence indicates that overweight and obesity are risk factors for end-stage renal disease. We aimed to elucidate the outcome of overweight IgAN patients and improve our ability to predict the progression of IgAN based on a combination of body mass index (BMI) and histopathological parameters, including maximal glomerular area (Max GA).
Methods: Forty-three adult IgAN patients whose estimated glomerular filtration rate was ≥50 ml/min/1.73 m(2) were enrolled in this study. Renal biopsy specimens were evaluated according to the Oxford classification of IgAN. A Kaplan-Meier analysis and the multivariate Cox proportional hazards method were used to evaluate 10-year kidney survival and the impact of covariates. The ability of factors to predict the progression of IgAN was evaluated by their diagnostic odds ratio (DOR).
Results: A BMI ≥25 kg/m(2) was found to be an independent predictor of a ≥1.5-fold increase in serum creatinine value (DOR 7.4). The combination of BMI ≥25 kg/m(2), Max GA ≥42,900 μm(2), and presence of mesangial hypercellularity (Oxford M1) optimally raised predictive power for disease progression of IgAN (DOR 26.0).
Conclusion: A combination of BMI ≥25 kg/m(2), the Oxford classification M1, and a Max GA ≥42,900 μm(2) can serve as a predictor of long-term renal outcome of IgAN.