ANCA Renal Risk Score in a Portuguese Cohort: Insights and Comparison with Berden Classification

Introduction: Antineutrophil cytoplasmic antibody (ANCA) ‑associated vasculitis (AAV) is a rare cause of glomerulonephritis. Despite advances in immunosuppressive therapies, AAV with renal involvement often leads to poor renal outcomes and a high ‑risk of end ‑stage renal disease (ESRD). Berden classification categorizes renal histology in four classes, but performance varies across cohorts. A lack of precise findings of prognostic value led to development of ANCA Renal Risk Score (ARRS). We assessed ARRS predictive value for renal survival in a Portuguese cohort and compared it to Berden classification. Methods: Observational and retrospective study analysing cases from native AAV kidney biopsies at a Portuguese histomorphology centre (2004 ‑2023). Demographical data, percentage of normal glomeruli, interstitial fibrosis/tubular atrophy and estimated glomerular filtration rate (eGFR) were recorded. Samples were categorized by Berden class and ARRS. Descriptive and comparative analyses were performed. Results: One hundred fifty eight patients, 53.8 % male, with mean age of 67.1 ± 14.1 years. Median ARRS was 6.5 ± 3.6, with 10.8%, 44.3% and 44.9% being low, intermediate, and high ‑risk, respectively. Overall mean time to dialysis was 20 months, renal survival at 36 months was 92.9%, 63.6% and 29.7% in low, intermediate and high ‑risk groups. Patient survival did not differ between groups. ROC curves showed statistical significance for both scores, with ARRS having the highest AUC (AUC <0.72, p<0.001 vs 0.65, p=0.03). Conclusion: ARRS was effective in predicting renal survival in this cohort, outperforming Berden classification in determining progression to ESRD at 36 months. Incorporating serum creatinine, treatment modalities and patient comorbidities could further improve ARRS predictive value.