Use and reporting of outcome measures in randomized trials for anti-neutrophil cytoplasmic antibody-associated vasculitis: a systematic literature review of randomized trials

Background: A comprehensive review of outcome measures used in randomized controlled trials (RCTs) of ANCA-associated vasculitis (AAV) could advance trial conductance for this disease. Methods: A systematic literature review of outcome measures (as specified in methods section as primary and/or secondary outcomes) in RCTs of AAV was conducted. Medline, Cochrane CENTRAL, and ClinicalTrials.gov were searched from inception until April 30, 2019 for RCTs enrolling patients with granulomatosis with polyangiitis and/or microscopic polyangiitis. Outcome measures were organized according to domains (e.g. disease activity) and instruments [e.g. Birmingham Vasculitis Activity Score (BVAS)]. Results: Out of 1101 identified records, 68 RCTs were eligible. Disease activity was an outcome domain collected in 67 (98%) of the RCTs. The BVAS was the most widely used instrument for disease assessment but definitions for remissions and relapse varied for the purpose of primary endpoint definitions. Damage, most often assessed by the Vasculitis Damage Index, was an outcome in 30 (44%) of the RCTs. Mortality was specified as an outcome in 26 (38%) studies. The following outcome domains were assessed: patient-reported outcomes (PROs) in 28 (41%), drug exposure/safety in 58 (85%), and biomarkers [acute phase reactants, ANCA levels] in 24 (35%). Timing for outcome assessment differed substantially, with 3, 6, or 12 months being the most frequent time points. Conclusion: Outcome measures used in AAV trials commonly included vasculitis-specific tools for disease assessment, but with heterogeneity in endpoint-definitions and timing of assessments. Other core outcomes in AAV, including PROs, and damage measures, are often omitted in AAV trials.