Objectives To prospectively evaluate the impact and the rapidity of the effect of mepolizumab on the ANCA-associated vasculitis patient-reported outcomes (AAV-PRO) questionnaire and patient global assessment (PtGA) in an international, multicentre cohort of patients with eosinophilic granulomatosis with polyangiitis (EGPA). Methods Patients with active EGPA initiating treatment with mepolizumab were included. PtGA and the AAV-PRO score were assessed at baseline and after 7, 14, 30, 90 and 180 days. Predictors of response of the AAV-PRO questionnaire were investigated. Results Seventy patients were included: female 54.3%, median age 56 years (48-65), 63 (90%) with a relapsing/refractory course. PtGA showed a statistically significant decrease within 7 days. At 14 days, all the AAV-PRO domains, except treatment side effects, showed a statistically significant decline. The improvement at 6 months was greatest in organ-specific symptoms (ratio 0.53), physical function (ratio 0.57) and PtGA (ratio 0.58). PtGA and higher disease activity positively correlated with the AAV-PRO scores throughout the study. Female patients reported a greater burden in terms of systemic symptoms, treatment side effects, social and emotional impact and concerns about the future. Conversely, age, educational level, damage accrual, mepolizumab dose and ANCA status had no effect on the AAV-PRO scores. Conclusions Mepolizumab was associated with a quick and remarkable improvement of health-related quality of life in patients with EGPA. These findings highlight its early and sustained benefits beyond disease control and support the integration of the AAV-PRO questionnaire into routine clinical practice.
