Kidney biopsy as a predictor for renal outcome in ANCA-associated necrotizing glomerulonephritis

Background. In kidney biopsies of patients with anti-neutrophil cytoplasmic antibody (ANCA)-associated systemic vasculitis: a variety of histopatholog ical lesions occur, and their relationship to renal outcome is virtually un known. This multicenter European study reports a clinicopathological analys is of biopsies from 157 patients with systemic vasculitis. Methods. The biopsies were evaluated according to a previously standardized scoring protocol. Serum creatinine values were measured at the time of bio psy and one year later. In addition, the lowest creatinine level during fol low-up was taken into account as the optimum level of renal function recove ry. The clinical prognostic value of the histopathological parameters was a nalyzed with the Kruskal-Wallis one-way analysis of variance and the Mann-W hitney Li-test. Results. The percentage of normal glomeruli correlated most significantly w ith renal outcome at all points of measurement (all P < 0.001). Other lesio ns predicting for renal function were glomerular sclerosis (P < 0.0005 at o ne year after the biopsy), diffuse interstitial infiltrates (P < 0.0001 at entry, P < 0.0003 at one year), tubular necrosis (P < 0.0025 at entry), and tubular atrophy (P < 0.002 at entry, P < 0.0002 at one year). Conclusion. Traditionally, attention is focused on the extent of active les ions in the renal biopsy in order to determine the severity of renal diseas e and its implication for renal outcome. Because of their significant impac t on renal function: combined with their easy recognition, we recommend the use of the percentage of normal glomeruli in an adequate biopsy in predict ing renal function of patients with systemic vasculitis.