#2257 Kidney outcomes in ANCA-associated vasculitis—application of Berden's Classification and ANCA Renal Risk Score in a single centre cohort
Authors: Alexandre Ines , Curto Andreia , Henriques Fábio , Brás Ana Catarina , Serra Maria Adelaide , Santos Joana , Manso Rita , Pires Ana , Carrilho Patrícia , Domingos Fernando 
Published: May 2024

Abstract

Background and Aims
Anti-neutrophil cytoplasmic antibody (ANCA) -associated vasculitis is the most common cause of rapidly progressive glomerulonephritis and is a life-threatening condition. The course of the disease is variable and disease prognostication remains challenging. Histological and clinical scores have been developed to predict kidney outcomes, to tailor treatment.
The aim of this study is to apply Berden´s histopathological classification (BHC) and ANCA renal risk score (ARRS), proposed by Brix and co-workers, in a cohort of patients with ANCA-associated vasculitis and to analyse their performance in renal outcomes prediction.

Method
In this retrospective observational study, we included patients with biopsy proven ANCA-associated vasculitis, diagnosed at our centre between March 2011 and March 2023. We consulted the clinical records and the kidney biopsy reports. Biopsies were categorized according to both scores. Follow up time was up to 48 months since the date of diagnosis.
In BHC patients were divided into 4 groups (focal, crescentic, sclerotic and mixed) according to normal glomeruli, cellular crescents and globally sclerosed glomeruli proportion.
When applying the ARRS, patients were divided into 3 groups: low, medium or high risk. This is a histopathological and biochemical score that combines normal glomeruli and tubular atrophy and interstitial fibrosis (IFTA) percentages with estimated glomerular filtration rate (eGFR) at time of diagnosis.
Factors related to renal survival were evaluated by Spearman Rank Correlation, Binary Logistic Regression analysis and Kaplan-Meier curves were used for assessing time between diagnosis and end stage kidney disease (ESKD).

Results
Our study included 31 patients, 54.8% were male, median age at diagnosis was 62 (IQR, 53-69) years, with a median eGFR of 8.3 (IQR, 6.2-13.3) mL/min/1.73 m2 and a median urine albumin to creatinine ratio (uACR) of 1.5 (IQR, 0.88-2.2) g/g. 19 patients (61.3%) were positive for myeloperoxidase and 5 (16.1%) were proteinase 3 positive. Median follow up time was 36 (IQR, 9-48) months. 10 patients (32%) developed ESKD and 9 patients (29%) died.
Regarding BHC, 4 patients (13%) presented a focal class, 18 (58%) crescentic, 7 (23%) mixed and 2 (6%) sclerotic. Progression to ESKD occurred in 7 patients with crescentic class (38.9%), 2 patients with mixed (28.6%) and 1 patient with sclerotic (50%). None of the patients with focal class developed ESKD. There were no significant differences in kidney survival curves by BHC class (Log Rank p = 0.47) (Fig. 1a).
In ARRS, 1 patient (3%) was in the low-risk group, 19 patients (61%) in the medium risk and 11 patients (35%) in the high risk. Characteristics of the population by ARRS score group and detailed score discrimination are specified in Table 1. Progression to ESKD, occurred in 5 patients of medium risk group (26.3%) and also in 5 patients in the high-risk group which represented 45.5% of this group. Kidney survival curves by ARRS score group had no statistic difference (Log Rank p = 0.46) (Fig. 1b).
ESKD was positively associated with serum creatinine (sCr) at admission (p = 0.02), highest sCr (p = 0.001) and leukocyturia (p = 0.05). By multivariate analysis adjusted to gender, age, sCr at admission, leukocyturia and BHC or ARRS, the only factor associated with ESKD was sCr at admission (OR 1.45, CI 1.03-2.06, p = 0.05).

Conclusion
In our cohort of patients, sCr at patient hospital admission was the best predictor for progression to ESKD. By ARRS, just one patient had low risk, and as expected, kidney survival was higher in the medium risk group (68.5%) than in the high-risk group (53%), although not reaching statistical significance. BHC also had no association with kidney outcomes, although kidney survival was 100% in focal class and sclerotic class had the lowest survival (50%), yet crescentic class revealed a worse kidney survival (57.1%) than mixed class (71.4%). The small number of patients, overall and in each group, and the short follow up period can be pointed as limitations of this study.