Validation study of the antineutrophil cytoplasmic antibody (ANCA) kidney risk score in Japanese patients with ANCA-associated glomerulonephritis.

In 2018, the Antineutrophil Cytoplasmic Antibody (ANCA) Renal Risk Score (ARRS) was proposed as a prognostic tool for renal outcomes in patients with ANCA-associated glomerulonephritis (AAGN). Subsequently, a revised version of the ANCA Kidney Risk Score (AKRiS) was reported in 2024. Nonetheless, its usefulness in Japanese patients has not yet been evaluated. We retrospectively analyzed 109 patients with biopsy-proven AAGN (mean age, 69 years; 50% male) from 13 institutions in Nagasaki Prefecture between January 1995 and December 2019. The prognostic performance of both the ARRS and AKRiS for end-stage kidney disease was assessed using Kaplan-Meier analysis, log-rank test, and receiver operating characteristic (ROC) curve analysis. Myeloperoxidase-ANCA positivity was observed in 90.8% of patients. Based on the AKRiS, 47, 39, 15, and 8 patients were classified as low-, medium-, high-, and very high-risk, respectively. The median observation period was 863 days (interquartile range 254.5-2034). Both the ARRS and AKRiS groups demonstrated progressively worse renal survival with increasing risk categories (both p < 0.001). In the ROC analysis, the area under the curve was 0.76 and 0.82 for ARRS and AKRiS, respectively. AKRiS may be a useful prognostic tool for renal outcomes in Japanese patients with AAGN, potentially providing better predictive accuracy compared to the ARRS.