Introduction

Physician-based measures for disease activity and damage are widely accepted tools for disease assessment in anti-neutrophil cytoplasmic antibodies (ANCA)-associated vasculitis (AAV) and have allowed for conduct of successful clinical trials that have refined use of existing therapeutic agents and identified new, effective medical therapies . Despite those advances, AAV remains associated with substantially reduced health-related quality of life (HRQoL), including during periods of disease remission . Therefore, ‘end’ points based purely on attainment or maintenance of remission, as currently defined, might not satisfy the next generation of randomised clinical trials (RCTs) in AAV. Outcome measure development for the large-vessel vasculitis is in an early stage . Future outcome measures need to both incorporate the patient perspective to capture treatment benefits of most importance to patients and have excellent statistical properties to maximise trial efficiency. Better statistical properties of outcome measures will allow for detecting smaller differences between treatment arms (of particular value in comparative effectiveness trials), allow for enrolment of fewer subjects, have more power to look at subgroups or allow for shorter follow-up times; these are all important considerations to allow for efficient testing of candidate therapeutic agents and are particularly important when studying rare diseases, such as the vasculitides.