Monitoring disease activity in eosinophilic granulomatosis with polyangiitis: a scoping review.

OBJECTIVES: Eosinophilic granulomatosis with polyangiitis (EGPA) is a rare vasculitis characterised by eosinophilic inflammation, asthma, and often anti-neutrophil cytoplasmic antibody (ANCA) positivity. Monitoring disease activity is challenging because conventional tools, mainly the Birmingham Vasculitis Activity Score (BVAS), account for manifestations not relevant to EGPA while insufficiently capturing respiratory and eosinophilic features.This scoping review aims to systematically evaluate current methods, biomarkers, imaging studies or other procedures to monitor disease activity or treatment response in EGPA. METHODS: Eligible studies were those published between January 2005 and March 2025, including at least five EGPA patients (≥10% of the cohort), and focusing on disease activity or treatment response. Non-human studies, case reports, reviews, and investigations focused on diagnosis were excluded. RESULTS: Of 874 records screened, 58 studies met inclusion criteria. Clinical studies frequently adopted MIRRA trial definitions of remission (BVAS=0, prednisone ≤4 mg/day), but criteria varied across studies, with the most adopted secondary endpoints being oral glucocorticoid sparing, changes in eosinophil count and in pulmonary function. Biomarker investigations explored conventional lab parameters as well as emerging molecular candidates, but none achieved consistent reliability in distinguishing active from inactive disease. Imaging and procedures such as pulmonary function tests, high-resolution CT, FeNO, echocardiography, and cardiac MRI showed promise but lacked validation. CONCLUSIONS: No robust tool currently exists for EGPA monitoring, even though interesting biomarkers and imaging techniques warrant further validation. Future research should prioritise harmonising definitions of remission and relapse, distinguishing systemic from organ-specific activity, and integrate clinical, biomarker, and imaging approaches to develop EGPAspecific monitoring strategies.