MPO and chronic rhinosinusitis: BMI: body mass index; BVAS: Birmingham Vasculitis Activity; CRS: chronic rhinosinusitis; CS: corticosteroid; CT: computed tomography; EGPA: eosinophilic granulomatosis with polyangiitis; ICS: inhaled corticosteroid; IS: immunosuppressant; MPO-ANCA: myeloperoxidase anti-neutrophil cytoplasmic antibody; MPZ: mepolizumab; NP: nasal polyp; OCS: oral corticosteroid; SNOT-22: 22-Item Sino-Nasal Outcome Test.