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Background and Aims Despite significant progress in treatment of ANCA-associated vasculitis (AAV), at least 20% of patients with renal involvement develop end-stage renal disease (ESRD). Histopathologic classification by Berden et al, which addresses only glomerular pathology, has been used to predict renal outcome in ANCA-assoicted glomerulonephritis (ANCA-GN) since 2010.1 In 2018 Brix et al proposed ANCA renal risk score (ARRS), which combines assessment of morphological (percentage of normal glomeruli, tubular atrophy and interstitial fibrosis) and clinical parameters (estimated glomerular filtration rate) to predict probability of ESRD.2 The aim of our study was to compare clinical utility of these two methods. Methods In our retrospective study we enrolled 57 patients with ANCA-associated vasculitis, diagnosed according to Chapel Hill Consensus Conference (2012) definition and/or American College of Rheumatology (1990) criteria, with histologically proven renal involvement. There were 14 (24.6%) males and 43 (75.4%) females, median age at AAV onset was 48 (33; 57) years. Fifty-one (89.5%) patients were ANCA-positive. Eight (14.0%) patients were diagnosed with renal-limited AAV. Median Birmingham vasculitis activity score (BVAS v.3) at onset was 16 (13; 19). In each case ANCA-GN class was established according to Berden classification: focal (>50% normal glomeruli); crescentic (>50% cellular crescents); mixed (50% globally sclerotic glomeruli). ARRS at onset was also retrospectively assessed and all patients were divided into three groups depending on the risk of ESRD: low risk (0 points), intermediate risk (2 to 7 points), or high risk (8 to 11 points). Thirteen patients (22.8%) developed ESRD after a median of 12 (6.5; 28) months. Renal survival rates were assessed by Kaplan-Meier method and compared by log-rank test. Results Among the 57 patients seven (12.3%) had focal, 10 (17.5%) – crescentic, 24 (43.2%) – mixed, and 16 (28.1%) – sclerotic ANCA-GN class according to Berden et al classification. 1- and 3-year renal survival rates were the highest (100% and 100% respectively) in focal, and the lowest in sclerotic class (67% and 50.2% respectively). 1- and 3- year renal survival was similar in crescentic (80% and 80% respectively) and mixed (80.6% and 80.6% respectively) classes (Fig. 1A). The differences were not statistically significant (Log-rank (Mantel-Cox) p = 0.17). Then we retrospectively re-evaluated all cases according to ARSS: 12 cases were classified as low-risk, 27 – as medium risk, 18 – as high risk. One-year and three-year survival rates were 100% and 100% in low-risk group, 86.1% and 74.2% in medium risk group, 50.6% and 50.6% in high risk group (Figure 1B). The differences were statistically significant (Log-rank (Mantel-Cox) p=0.003). Conclusion In our limited group of patients ANCA renal risk score classification provided better and more clear stratification of patients in terms of ESRD prediction than Berden classification. ARRS is a simple and valuable tool for assessment of renal survival prognosis which can contribute to personalized approach to the management of AAV.