Disease Activity, Glucocorticoid Exposure, and Rituximab Determine Body Composition Changes during Induction Treatment of ANCA-Associated Vasculitis

Introduction: We investigated the relationships between glucocorticoid (GC) use, disease activity, and changes in body mass index (BMI) in patients with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). Methods: We analyzed AAV patients enrolled in the Rituximab in ANCA-Associated Vasculitis (RAVE) trial. GC use, BMI, and disease activity were measured regularly during the trial period. We performed mixed effects regressions to examine the associations of time-dependent cumulative average GC use and disease activity with changes in body mass index (BMI) over time, while adjusting for potential confounders. Results: The baseline BMI among the 197 patients enrolled was 28.8 (±6.3) kg/m2. Patients with newly-diagnosed AAV tended to have a lower mean BMI compared to those with relapsing disease (28.0±5.7kg/m2 vs 29.6 ±6.8kg/m2) and a higher disease activity Birmingham Vasculitis Activity Score for Wegener's Granulomatosis (BVAS/WG, 8.7±3.3 vs 7.4±2.7). The most significant change in BMI occurred during the first six months of the trial (+1.1±2.2 kg/m2, P<0.0001). Disease activity improvement, GC exposure, and randomization to rituximab were each independently associated with increase in BMI (P<0.001 for all analyses). Discussion: Our findings suggest that changes in BMI are independently associated with improvements in disease activity as well as GC exposure in AAV. Rituximab may also have effects on BMI independent of its impact on disease activity. This article is protected by copyright. All rights reserved.