Comparison of Clinical and Histopathological Scoring Systems in a Japanese Cohort of Patients with ANCA-Associated Glomerulonephritis Diagnosed by Kidney Biopsy

Background: Predicting the prognosis of antineutrophil cytoplasmic antibody-associated glomerulonephritis (ANCA-GN), which presents diverse clinical manifestations, is essential for guiding appropriate treatment strategies. Several clinical and histopathological scoring systems have been proposed to estimate kidney outcomes in ANCA-GN. This study aimed to compare the performance of these scoring systems in a Japanese cohort of patients with ANCA-GN. Methods: We retrospectively analyzed 142 patients with biopsy-proven ANCA-GN from six hospitals in Japan. The primary composite outcome was a combination of end-stage kidney disease and all-cause mortality. We evaluated the predictive performance of three established classification/scoring systems: the Berden classification, the Japanese Clinical Grading System for rapidly progressive glomerulonephritis (RPGN), and the ANCA Renal Risk Score (ARRS). In addition, we externally validated two newer systems: the improved ANCA Kidney Risk Score (AKRiS) and the Percentage of ANCA Crescentic Score (PACS). Results: During a median follow-up of 2.9 years (interquartile range: 0.2–5.7), 47 composite events occurred. The areas under the receiver operating characteristic curve for predicting the primary outcome were as follows: Berden classification, 0.66 (95% CI: 0.57–0.75); Japanese RPGN Clinical Grade, 0.73 (0.64–0.81); ARRS, 0.82 (0.74–0.89); PACS, 0.77 (0.69–0.86); and AKRiS, 0.87 (0.79–0.94). Stratification by AKRiS risk categories revealed 5-year cumulative event-free survival rates of 89.8%, 52.9%, 27.7%, and 0%, respectively (P < 0.001). Conclusion: This study provides the first external validation of AKRiS and PACS in a Japanese ANCA-GN cohort. The revised AKRiS demonstrated superior performance in predicting hard outcomes compared to other existing scoring systems.