#1253 Predicting renal outcomes in ANCA-associated vasculitis—validation of ANCA Renal Risk Score in a Portuguese cohort

Abstract

Abstract Background and Aims Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a rare cause of glomerulonephritis and clinical presentation can be diverse. Despite recent developments in immunosuppressive treatments, AAV with renal involvement is still associated with poor renal prognosis and a high risk of end-stage renal disease (ESRD). Kidney biopsy confirms the diagnosis, details the degree of active inflammation and chronicity of disease, also informing of renal prognosis. Berden histological classification categorizes renal histological findings into four classes but the ability to accurately predict renal outcomes varies among studied cohorts. In 2018 Brix et al developed and validated a new risk score, ANCA Renal Risk Score (ARRS), to determine renal outcomes based on histopathological and clinical indicators, with accurate ESRD prediction at 36 months. This study aims to assess the predictive value of ARRS in renal survival on a Portuguese cohort with newly diagnosed AAV with kidney involvement. Method We designed a retrospective study examining ANCA vasculitis in native kidney biopsies evaluated in a Portuguese kidney histomorphology-dedicated center between 2004 and 2023. Data collected from biopsies included percentage of normal glomeruli (PNG) and interstitial fibrosis/tubular atrophy (IFTA). Clinical and demographical data was also collected, including age, sex, estimated glomerular filtration rate (eGFR) at presentation, date of diagnosis, ESRD and date of death. We calculated ARRS based on eGFR, PNG and IFTA, and patients were classified as being at low, intermediate and high risk of developing ESRD by 36 months. Primary endpoint was established as difference in kidney survival at 36 months. Secondary endpoint included difference in overall survival at 36 months and the contribution of each of the ARRS parameters in a Cox regression model. Results A total of 143 patients were obtained, 46.2% female, with a mean age at diagnosis of 67.1 years. There was a predominancy of MPO-related disease (77.2%) and 69% presented with rapidly progressive renal insufficiency. Median ARRS was 6.5, with 10.8%, 44.3% and 44.9% classified as low, intermediate, and high risk, respectively. Kaplan Meier estimates for renal survival computed at 36 months revealed an overall mean time to dialysis of 20 months, which decreased with an increase in risk category [33.4 (low risk), 24.7 (intermediate risk), 12.7 months (high risk), Log-R test: χ2(2) = 24.9, p < 0.001] with an ESRD survival of 92.9%, 63.6% and 29.7% at 36 months, respectively. Regarding secondary endpoints, overall survival at 36 months was not different between groups [33.7 (low risk) vs. 33.2 (intermediate risk) vs. 32.2 months (high risk), Log-R test: χ2(2) = 0.3, p = 0.9]. Cox regression, plotted for ESRD at 36 months using the three score variables, revealed eGFR at presentation as the strongest predictor of kidney survival (HR: 0.96, 95% CI: 0.93-0.99, p = 0.004) whereas PNG and IFTA did not achieve significance (p = 0.189 and p = 0.066, respectively). Conclusion Our results corroborate Brix et al ARRS, accurately predicting ESRD in a Portuguese cohort of patients with renal involvement by ANCA vasculitis. Patients assessed as high-risk of developing ESRD had a lower mean time to dialysis, although overall survival did not differ between groups. Contrary to Brix et al findings, which revealed PGN as the only independent predictor of ESRD, in our study lower eGFR at the time of diagnosis was an independent risk factor. Type of immunosuppression used in each patient was not considered in this study and could maybe alter results of renal and overall survival. Despite this, Brix et al reported that, in their population, validity of ARRS was not influenced by immunosuppressive treatment. This new scoring system still requires validation in a larger cohort, but results seem promising and, in the future, may aid clinicians with treatment decisions. This is relevant since full immunosuppression induction schemes may be halted in patients with high probability of ESRD, diminishing infectious complications and potentially decreasing morbidity and mortality associated with AAV.