Kinetic eGFR Ratio Predicts Active Lesions and Prognosis in ANCA-Associated Glomerulonephritis

Background: Antineutrophil cytoplasmic antibody-associated glomerulonephritis (ANCA-GN) is a typical vasculitis syndrome presenting with rapidly progressive glomerulonephritis (RPGN). Kinetic estimated Glomerular Filtration Rate (KeGFR) has been proposed to approximate true GFR under non-steady-state conditions. We investigated the clinicopathologic and prognostic significance of KeGFR in patients with ANCA-GN. Methods: We retrospectively identified 66 patients with ANCA-GN from 3 hospitals in Japan (2004–2020). KeGFR ratio was defined as the ratio of KeGFR difference to baseline eGFR. The primary composite endpoints included end-stage kidney disease and death. We compared clinicopathologic features and long-term outcomes between the high KeGFR ratio group and the low KeGFR ratio group. We also assessed the factors associated with treatment resistance. Results: Patients with a high KeGFR ratio had a higher incidence of treatment resistance and a higher percentage of cellular crescents and interstitial inflammation (Tables 1 and 2). The cumulative event-free survival rate at 5 years was significantly lower in the high KeGFR group than in the low KeGFR group (Figure 1). In addition, the KeGFR ratio was significantly associated with treatment resistance after adjusting for age, ANCA renal risk score (which included % normal glomeruli, baseline eGFR, and % Interstitial fibrosis/tubular atrophy), and treatment (Table 3). Conclusion: KeGFR ratio is associated with disease state and acute lesions in ANCA-GN and may be useful in assessing long-term prognosis and treatment resistance.Table 1. and Table 2.Figure 1. and Table 3.