Background/Objectives: Berden´s histopathologic glomerulonephritis (GN) classification in ANCA vasculitis is based on glomerular damage 1. The ANCA renal risk score (ARRS) 2 is a prognostic renal score that takes into account percentage of normal glomeruli (<10/10-25/>25%), percentage of tubular atrophy/interstitial fibrosis (< or > 25%) and glomerular filtration rate (< or > 15 ml/min), with a score from 0-11, and classifies patients into groups at low (0-1 points), medium (2-7 points) or high risk (8-11 points) of end-stage renal disease (ESRD). Our objective was to evaluate the performance of the ANCA renal risk score in patients with ANCA vasculitis and renal involvement seen at our hospital. Methods: Observational retrospective study. Patients ≥ 18 years with biopsy-proven ANCA GN were included between 2002 and 2020. Demographic and clinical data were collected from electronic medical records. Renal biopsies were classified according to Berden classification (focal, crescentic, mixed, and sclerotic class). ARRS was calculated at diagnosis. Renal survival, defined as dialysis/transplant-free patients, was evaluated at 6, 12 and 36 months. ROC curves were performed to evaluate the diagnostic accuracy of ARRS. Univariate predictors of renal survival, including the different histological classes and ARRS subgroups, were evaluated using Kaplan-Meier method and Cox proportional hazard model. Results: Eighty-seven patients with ANCA GN were included: 26 granulomatosis with polyangiitis, 25 microscopic polyangiitis, 4 eosinophilic granulomatosis with polyangiitis and 32 renal-limited vasculitis. Mean age at diagnosis was 65.5 years (SD 16.2), and median follow-up time after renal biopsy was 3.7 years (IQR 1.5-6.5). According to Berden classification, 27 patients had a focal class, 25 crescentic, 22 mixed and 13 sclerotic class in renal biopsy. Sixteen patients (19.5%) died during follow-up. Renal failure was present in 9, 7 and 6 patients at 6, 12 and 36 months respectively, none of whom had a focal class biopsy. Area under ROC curve for ARRS in relation to renal failure at 6, 12 and 36 months was 0.92 (95% CI 0.83-1.00), 0.90 (95% CI 0.79-1.00), and 0.93 (95% CI 0.82-1.00) respectively (figure 1). The best cut-off point in ARSS for predicting renal failure was ≥ 9 with a sensitivity and specificity of 88.9% and 89.9% at 6 months, 85.7% and 86.9% at 12 months, and 83.3% and 93.0% at 36 months. None of the patients with a low or medium ARRS (<8 points) developed ESRD during follow-up. In the univariate analysis, ARRS, as a continuous variable, was associated with renal failure at 6 months (HR 1.75, 95% CI 1.24-2.47, p = 0.001), 12 months (HR 1.82, 95% CI 1.22- 2.70, p = 0.003) and 36 months (HR 1.75, 95% CI 1.17-2.62, p = 0.006). Conclusions: In this cohort of patients with ANCA GN, the ARRS demonstrated a very good discriminatory capacity, sensitivity and specificity to predict renal failure at 6, 12 and 36 months. Disclosures: none.