The predictive value of kidney biopsy in renal vasculitis: a multicenter cohort study

The histopathologic classification of antineutrophil cytoplasmic antibody-associated vasculitis has been demonstrated to have prognostic value in small cohorts of patients with pauci-immune extracapillary glomerulonephritis. We aimed to validate this histologic subgrouping system in a large cohort of patients with renal vasculitis from 3 Spanish centers. The additional value of several histologic parameters for predicting renal outcome was investigated. A total of 151 biopsies of patients with renal vasculitis were reviewed and classified as follows: 41% crescentic, 24% mixed, 21% focal, and 14% sclerotic. The cumulative proportions of renal survival at 5 years were 83.2%, 81.2%, 60.5%, and 50.7% for the focal, mixed, crescentic, and sclerotic categories, respectively (P < .05). In the crescentic category, patients with less than 75% of glomeruli showing crescents had better survival at 1 and 5 years compared with those having greater than or equal to 75% of crescents (77.9% and 70.6% versus 51.3% and 45.6%; P = .02). When adjusted by renal function and other histologic parameters, the percentage of extracapillary proliferation and glomerulosclerosis remained as significant predictors for renal survival (hazard ratio, 1.03; 95% confidence interval, 1.01-1.05; P = .001, and hazard ratio, 1.03; 95% confidence interval, 1.01-1.05; P = .002, respectively). In conclusion, patients with pauci-immune crescentic glomerulonephritis experienced different outcomes depending on the percentage of crescents observed, so that extensive extracapillary proliferation was associated with the poorest renal survival. These findings validate the prognostic utility of the histologic classification scheme in antineutrophil cytoplasmic antibody positive and negative patients and suggest a subdivision of crescentic category (<75% and ≥75% of crescents) based on the different survival rates observed among these subgroups.