Glomerular Density in Renal Biopsy Specimens Predicts the Long-Term Prognosis of IgA Nephropathy

Background and objectives: An early histopathologic predictor of the renal prognosis, before the occurrence of advanced glomerular sclerosis/interstitial fibrosis and/or apparent renal dysfunction, remains to be established in IgA nephropathy (IgAN). This study aimed to determine whether the glomerular density (GD; nonsclerotic glomerular number per renal cortical area) of biopsy specimens obtained at an early stage of IgAN could predict the long-term renal outcome. Design, setting, participants, & measurements: The predictive value of the factors at biopsy, including the GD, on the renal outcome was retrospectively analyzed for 98 patients who had IgAN with an estimated GFR of >= 60 ml/min per 1.73 m(2) at biopsy (87 ml/min per 1.73 m(2) on average). Results: The individual value of GD in biopsy ranged from 1.2 to 8.1/mm(2) (i.e., approximately a seven-fold variation), and the GD showed a close inverse correlation with mean glomerular volume. Among the various clinicopathologic factors involved, both a cellular/fibrocellular crescent and the GD were found to be significant predictors of progression in multivariate analyses. A low GD in the biopsy specimens was frequently associated with a steeper slope of the renal function and a synergistically enhanced risk for progression with the presence of cellular/fibrocellular crescent. The renal function, proteinuria, degrees of glomerulosclerosis, and interstitial fibrosis at biopsy were not independent predictors of the prognosis in these patients. Conclusions: A strong predictive relationship of low GD with progression observed in this study suggests that GD may serve as an early histopathologic marker of long-term renal prognosis in IgAN. Clin J Am Soc Nephrol 5: 39-44, 2010. doi: 10.2215/CJN.04680709