#988 The impact of kidney relapse on long-term kidney function in ANCA-associated vasculitis

Abstract Background and Aims ANCA-associated vasculitis (AAV) often results in chronic kidney disease (CKD) and progresses to end-stage kidney disease (ESKD). Long-term trajectories of kidney function and the impact of kidney relapse on these trajectories in AAV are not well defined. This study evaluated long-term kidney function before and after kidney relapse and compared the trajectories to those of patients without relapse, using data from the PEXIVAS trial of plasma exchange and glucocorticoid dosing. Method This post-hoc analysis of the PEXIVAS trial included patients with kidney involvement at baseline who achieved remission prior to 12 months and had at least 2 subsequent estimated glomerular filtration rate (eGFR) assessments. Patients who developed ESKD before 12 months or those without eGFR data beyond 12 months were excluded. We calculated eGFR slopes of patients who did not experience kidney relapse as well as pre- and post-relapse slopes of patients who had kidney relapse at least 12 months after randomisation. We additionally compared the group mean eGFRs at each follow-up time. To create a common time to compare eGFR relative to the time of relapse, Time 0 was defined as: (i) time of relapse for relapsers and (ii) time corresponding to the month of relapse of their matched relapsers for non-relapsers. Patients were matched using propensity scores based on sex, ANCA subtype, eGFR at randomisation and time of enrolment. A linear mixed-effects model was employed to estimate eGFR slope, with adjustment for the main effects of age, sex, ANCA subtype, eGFR at randomisation, and their interactions with time. Results Of 704 participants in PEXIVAS, 459 were included, of whom 51 (11.1%) had a kidney relapse after 12 months (median time to relapse: 847 days). Baseline characteristics were comparable between those with and without kidney relapse, including median eGFR at randomisation (17.2 vs 19.2 ml/min/1.73 m2; P = 0.76) and at 12 months (41.3 vs 42.7 ml/min/1.73 m2; P = 0.37) (Table 1). The mean eGFR in patients that relapsed was lower at and after relapse compared to those that did not relapse (Fig. 1). The overall slope in the non-relapse group was 0.7 (95% CI: −0.3 to 1.8) mL/min/1.73 m2/year. In the relapse group, the pre-relapse slope was −5.9 (95% CI: −10.2 to −1.5) mL/min/1.73 m2/year, while the post-relapse slope was −1.1 (95% CI: −3.8 to 1.6) mL/min/1.73 m2/year. After adjustment, the pre-relapse slope was −6.9 (95% CI: −10.6 to −3.2) mL/min/1.73 m2/year and the post-relapse slope was −2.3 (95% CI: −4.6 to 0.1) mL/min/1.73 m2/year. The eGFR slope differed between the relapse and non-relapse groups during the pre-T0 period (P = 0.018), whereas no difference was observed in the post-T0 period (P = 0.10). Conclusion Kidney relapse in AAV occurring after 12 months of treatment initiation was preceded by a decline in eGFR, and was associated with long-term decline in kidney function. Those with no relapse demonstrated a stable eGFR over time. Early identification and treatment of kidney relapses in AAV may improve long-term kidney function.

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