Table 1

Study inclusion and exclusion criteria

Inclusion criteriaExclusion criteria
  1. Full length, peer-reviewed original studies using the Delphi method with international participants to develop a COS

  2. Protocols for studies using international Delphi surveys to develop a COS (may be non-peer-reviewed)

  1. Articles that were not published within the accepted date range: 1 January 2017–6 June 2019

  2. Articles not written in English

  3. Articles that were not full-text and peer-reviewed (with the exception of protocol studies)

  4. Articles that do not report development of a COS for a medical condition or intervention for the purposes of clinical trial reporting

  5. Articles that do not report using a Delphi survey

  6. Articles that do not report using an ‘international’ Delphi survey (members of at least one of the following groups should be described as international: patients, patient representatives or healthcare professionals)

  • COS, core outcome set.