Association of the ANCA Kidney Risk Score with kidney failure in anti-GBM disease

Introduction Anti-glomerular basement membrane (anti-GBM) disease is a rare vasculitis that is characterized by a poor renal prognosis. Despite the high predictive accuracy of the improved ANCA Kidney Risk Score (AKRiS) in ANCA-associated vasculitis, its prognostic value in anti-GBM disease remains to be established. Methods In this multicenter retrospective study, 163 biopsy-proven anti-GBM patients were included. AKRiS was calculated at diagnosis, stratifying patients into low-, moderate-, high-, and very high-risk groups. The Fine-Gray model was used for the analysis of 36-month kidney failure, with the predictive performance assessed via Harrell's C-index. Results The median AKRiS was 18 [11–21], with 69% of patients classified as high or very high-risk. The 36-month cumulative incidence of kidney failure was significantly higher in the high- (92% [95%CI: 82–97]) and very high-risk (98% [95%CI: 86–100]) groups, when compared to the low-risk (40% [95%CI: 19–61]; p<0.0001). In the multivariable analysis, AKRiS was independently associated with a poor renal prognosis (sHR 2.51 and 2.82 for the high- and very high-risk groups vs. low-risk, respectively). The model combining oligoanuria and AKRiS improved the predictive performance of AKRiS alone (C-index 0.90 [95%CI: 0.85–0.94] vs 0.85 [95%CI: 0.80–0.91]; p=0.02). Despite higher AKRiS scores, double-positive patients had similar 36-month kidney failure compared to single-positive patients, reflecting their divergent pathophysiological and therapeutic responsiveness. Conclusion AKRiS is associated with renal risk in anti-GBM disease, irrespective of ANCA status. Its predictive performance further improves when combined with oligoanuria, supporting the development of pragmatic prognostic models for anti-GBM disease.