Published core outcome sets
Twenty completed COS development studies were identified (table S6) (17-20, 84-99) including: 13 (65%) in pregnancy and childbirth, 3 (15%) in newborn and neonatal health, 2 (10%) in benign gynaecology and subfertility and 2 (10%) in oncology. Sixteen studies (80%) were developed in an international context. All used the modified Delphi method to identify core outcomes. Delphi survey participants included healthcare professionals (range 34–154 participants), researchers (range 0-53), and patients (range 0–244 participants). Total number of participants included in the Delphi process ranged from 24 to 412. Twelve (60%) studies discussed the limitation of attrition bias, 2 comparing the mean results of non/responders between rounds to determine effect and 1 performed an attrition analysis to determine effect. Seventeen (85%) arranged consensus development meetings to finalize the core outcome set. Consensus meeting participants included healthcare professionals (range 5–17 participants), researchers (range 2-10), and patients (range 2–10 participants). All publications identified the study as a COS development process; the COMET registration number allowing researchers to identify the study within the database was stated in 15 (75%). Fifteen (75%) clearly defined their scope, including the health condition, intervention and setting for which the core outcome set was applied. Thirteen (65%) adequately described their methods identifying potential core outcomes; deviations from the protocol were reported in six (30%). Eighteen (90%) involved patients and or patient representatives as stakeholders in the consensus process. Four (20%) used qualitative research methods (interviews or systematic reviews) to explore the views of patients when generating the initial list of outcomes for inclusion in the consensus process. The number of outcomes entered into the Delphi process ranged from 15 to 263, with final number of core outcomes ranging from six to 48. Overall four COS (20%) fulfilled full criteria for COS‐STAD and three (15%) for COS-STAR. (table S3)