Renal outcomes in ANCA-associated vasculitis without clinically apparent kidney involvement: a multicentre REVEAL cohort study.

Abstract

Most studies on renal outcomes in ANCA-associated vasculitis (AAV) focus on GN; however, the prognosis of patients without clinically apparent kidney involvement is understudied. We aimed to characterize kidney prognosis in this overlooked subgroup. Estimated glomerular filtration rate (eGFR) trajectories by kidney Birmingham Vasculitis Activity Score (BVAS; 0 vs ≥1) were analysed. The primary outcome was incident chronic kidney disease (CKD) in the kidney BVAS = 0 group, defined as at least two eGFR values <60 ml/min/1.73 m2 obtained at least 90 days apart, accompanied by a decline ≥30% from baseline. The cohort included 129 patients with kidney BVAS = 0 and 228 with kidney BVAS ≥ 1. After remission induction, eGFR improved in kidney BVAS ≥ 1 but declined in kidney BVAS = 0; this worsening trajectory in the kidney BVAS = 0 group was observed regardless of treatment intensity. Over 3 years, incident CKD occurred in 30 patients in kidney BVAS = 0 (cumulative incidence 30.7%, 95% CI 21.6-42.6%). In Cox models, older age and higher baseline-to-1-month time-weighted average CRP (TWA-CRP) were associated with incident CKD. Baseline-to-1-month TWA-CRP predicted incident CKD (age-adjusted HR 1.21; 95% CI 1.06-1.39; P < 0.01), and TWA-CRP from 1 to 6 months ≥0.5 mg/dl at the 6-month landmark identified higher risk (HR 2.61; 95% CI 1.01-6.78; P = 0.049). In AAV without clinically apparent kidney involvement, TWA-CRP, as a surrogate of sustained systemic inflammation, was associated with incident CKD. Even with unremarkable urinalysis, eGFR monitoring is warranted.