Background: Recently, - “the Renal Risk Score” (RRS) has been proposed to evaluate the risk of end-stage kidney disease (ESKD) in (ANCA)-associated glomerulonephritis (ANCA-GN). However, few studies have compared the value of RRS and the histopathological classification in the same population. Besides, the factors associated with eGFR recovery after the onset of ANCA-GN have been poorly studied. Thus, the aim of the present study was first to analyze and compare the value for ESKD prediction of RRS and histopathological classification in a large and well phenotyped cohort. Next, we analyzed the factors associated with eGFR variations within the first two years following ANCA-GN diagnosis. Methods: We used the Maine-Anjou ANCA-associated vasculitis (AAV) registry, which, since January 2000, has gathered data on all consecutive patients diagnosed with ANCA-GN in 4 French Nephrology Centers. All adult patients with kidney biopsy performed at ANCA-GN onset showing pauci-immune crescentic GN and with at least 6 months of follow-up were included. Renal biopsies were reviewed and scored for the purpose of the study. The prognostic value of AAV histopathological classification and of RRS was evaluated in the cohort. Then, factors associated with eGFR variations between ANCA-GN diagnosis and 2 years of follow-up were studied. Results: Among the 180 patients of the registry, 123 could be included for the analysis of both histopathological classification and RRS predictive values for ESKD (“ESKD prognosis cohort”). Among the 123 patients, 80 had full eGFR data during follow-up and were included in the “eGFR cohort”. The initial median eGFR of the ESKD cohort was 17.9 mL/min/1.73 m2, 22.8% required renal replacement therapy at ANCA-GN onset and 33.3% developed ESKD after a median follow-up of 42 months. Twenty-nine patient were classified within focal, 25 within crescentic, 50 within mixed and 19 within sclerotic histopathological classes, while 40 patients were classified in low, 55 in medium and 28 in high RRS classes. The predictive value of RRS for ESKD was greater than histopathological classification. In the eGFR cohort the median eGFR increased from ANCA-GN diagnosis to month 6 and stabilized thereafter. Neither renal histological lesions at ANCA-GN diagnosis nor RSS value were associated with eGFR variation after 2 years. The only factor associated with eGFR variation was eGFR at ANCA-GN diagnosis, with higher eGFR at diagnosis being associated with eGFR loss (p<0.001). Conclusions: This study confirms the better predictive value of RRS as compared to histopathological classification for ESKD prediction. The main determinant of eGFR variation was eGFR at ANCA-GN onset. Thus, the present study suggests that eGFR recovery is poorly dependent of the severity of histological damage at ANCA-GN diagnosis. Disclosures: The authors declare that they have no conflicts of interest in relation to this abstract.