Abstract
There has been a marked increase in the past 15 years in the number and quality of clinical trials in the idiopathic inflammatory vasculitides, especially the small-vessel vasculitides known as antineutrophil cytoplasmic autoantibody (ANCA)-associated vasculitis [AAV; granulomatosis, with polyangiitis (Wegener's)]. These trials have been conducted by multicenter, international groups in Europe and the United States with financial support provided by government agencies and biopharmaceutical companies. This increased clinical trial activity in vasculitis has been accompanied by the development and validation of new outcome measures--a challenging process for these complex, multiorgan system diseases. The international OMERACT Vasculitis Working Group has developed and implemented an iterative research agenda that has utilized accumulated experience and datasets from several multicenter clinical trials and large cohort studies. This work has led to the development, evaluation, validation, and endorsement, through the OMERACT consensus and validation processes, of a "core set" of outcome measurements for use in clinical trials of AAV. The core set includes domains of disease activity, damage assessment, patient-reported outcomes, and mortality; there is at least one validated outcome measurement instrument available for each domain. This report reviews the domains of illness in AAV included in the OMERACT core set, describes the instruments validated to measure these domains, and presents the approved core set.