Estimating renal survival using the ANCA-associated GN classification

Abstract

A histopathological classification system for ANCA-associated vasculitis was recently published, but whether this system predicts renal outcome requires validation. Here, we analyzed data from 164 consecutive patients with biopsy-proven renal involvement of ANCA-associated vasculitis. The ANCA-associated GN (AGN) classification categorizes patients as having focal, mixed, crescentic, or sclerotic GN. Five-year renal survival rates by categories of the AGN classification scheme were 91% for focal, 69% for mixed, and 64% for crescentic (log-rank P<0.0001). Only one patient was classified as sclerotic. Furthermore, the percentage of normal glomeruli found on biopsy estimated renal survival with the same precision as did the AGN classification scheme. Patients classified as crescentic or mixed, however, had worse survival when the percentage of normal glomeruli was <25%. In conclusion, the AGN classification for renal biopsy specimens is a practical and informative scheme with which to categorize patients with ANCA-associated vasculitis, but adding the percentage of normal glomeruli to the system seems to improve its predictive value.

Figure 1.

Renal survival, as shown by AGN classification, is best in the focal group (log rank analysis P<0.0001). The sclerotic group was left out because it consisted of only one patient.

Figure 2.

Renal survival, as shown by percentage of normal glomeruli in the renal biopsy specimen, is best in patients with ≥75% and worst in patients with ≤25% normal glomeruli in the renal biopsy specimen (log rank analysis P<0.0001).

Figure 3.

Renal survival of patients classified as crescentic and mixed by the AGN classification is worse in patients with <25% normal glomeruli (log rank analysis P=0.04).