Systematic review of international Delphi surveys for core outcome set development: representation of international patients

OBJECTIVES: A core outcome set (COS) describes a minimum set of outcomes to be reported by all clinical trials of one healthcare condition. Delphi surveys are frequently used to achieve consensus on core outcomes. International input is important to achieve global COS uptake. We aimed to investigate participant representation in international Delphi surveys, with reference to the inclusion of patients and participants from low and middle income countries as stakeholders (LMICs). DESIGN: Systematic review. DATA SOURCES: EMBASE, Medline, Web of Science, COMET database and hand-searching. ELIGIBILITY CRITERIA: Protocols and studies describing Delphi surveys used to develop an international COS for trial reporting, published between 1 January 2017 and 6 June 2019. DATA EXTRACTION AND SYNTHESIS: Delphi participants were grouped as patients or healthcare professionals (HCPs). Participants were considered international if their country of origin was different to that of the first or senior author. Data extraction included participant numbers, country of origin, country income group and whether Delphi surveys were translated. We analysed the impact these factors had on outcome prioritisation. RESULTS: Of 90 included studies, 69% (n=62) were completed and 31% (n=28) were protocols. Studies recruited more HCPs than patients (median 60 (IQR 30–113) vs 30 (IQR 14–66) participants, respectively). A higher percentage of HCPs was international compared with patients (57% (IQR 37–78) vs 20% (IQR 0–68)). Only 31% (n=28) studies recruited participants from LMICs. Regarding recruitment from LMICs, patients were under-represented (16% studies; n=8) compared with HCPs (22%; n=28). Few (7%; n=6) studies translated Delphi surveys. Only 3% studies (n=3) analysed Delphi responses by geographical location; all found differences in outcome prioritisation. CONCLUSIONS: There is a disproportionately lower inclusion of international patients, compared with HCPs, in COS-development Delphi surveys, particularly within LMICs. Future international Delphi surveys should consider exploring for geographical and income-based differences in outcome prioritisation. PROSPERO REGISTRATION NUMBER: CRD42019138519.