Predictors of renal survival in ANCA-associated vasculitis. Validation of a histopatological classification schema and review of the literature.

OBJECTIVES: In 2010 a histopathological classification of ANCA-associated glomerulonephritis was proposed to predict the outcomes at diagnosis. Our aim was to validate the proposed classification in our cohort of patients and to compare the studies already published.
METHODS: The data of 93 patients who underwent kidney biopsy in a single Italian centre within 15 years were retrospectively collected.
RESULTS: The 10-year renal and patients' survival were 60% and 81%, respectively. Biopsies were classified as 21% focal, 30% crescentic, 39% mixed and 10% sclerotic. Survival without ESRD at 5 years was 82% in focal, 37% in crescentic, 81% in mixed and 51% in sclerotic group. The Kaplan-Meier analysis highlights that renal survival was not different between sclerotic and crescentic groups (p=0.9) but both had a significantly worse prognosis than focal (p=0.04 and 0.015 respectively) and mixed groups (p=0.05 and 0.03 respectively). Focal and mixed groups had the same renal survival (p=0.7). At multivariate analysis the independent predictors of end-stage renal disease were less than 20% of normal glomeruli at kidney biopsy (p=0.022), high serum creatinine (p=0.009) and arterial hypertension at presentation (p= 0.006).
CONCLUSIONS: In our cohort, the proposed histological classification was not predictive of renal prognosis. The focal and the mixed classes had the same prognosis and a significantly better renal outcome than both the crescentic and the sclerotic classes. At multivariate analysis among the histological features only less than 20% of normal glomeruli defines the renal prognosis together with renal function and arterial hypertension at baseline.