title: The use of qualitative methods to inform Delphi surveys in core outcome set development.
abstract: BACKGROUND
  Core outcome sets (COS) help to minimise bias in trials and facilitate evidence synthesis. Delphi surveys are increasingly being used as part of a wider process to reach consensus about what outcomes should be included in a COS. Qualitative research can be used to inform the development of Delphi surveys. This is an advance in the field of COS development and one which is potentially valuable; however, little guidance exists for COS developers on how best to use qualitative methods and what the challenges are. This paper aims to provide early guidance on the potential role and contribution of qualitative research in this area. We hope the ideas we present will be challenged, critiqued and built upon by others exploring the role of qualitative research in COS development. This paper draws upon the experiences of using qualitative methods in the pre-Delphi stage of the development of three different COS. Using these studies as examples, we identify some of the ways that qualitative research might contribute to COS development, the challenges in using such methods and areas where future research is required.
  
  
  RESULTS
  Qualitative research can help to identify what outcomes are important to stakeholders; facilitate understanding of why some outcomes may be more important than others, determine the scope of outcomes; identify appropriate language for use in the Delphi survey and inform comparisons between stakeholder data and other sources, such as systematic reviews. Developers need to consider a number of methodological points when using qualitative research: specifically, which stakeholders to involve, how to sample participants, which data collection methods are most appropriate, how to consider outcomes with stakeholders and how to analyse these data. A number of areas for future research are identified.
  
  
  CONCLUSIONS
  Qualitative research has the potential to increase the research community's confidence in COS, although this will be dependent upon using rigorous and appropriate methodology. We have begun to identify some issues for COS developers to consider in using qualitative methods to inform the development of Delphi surveys in this article.
authors.affiliation: Centre for Patient Reported Outcomes Research, Institute of Applied Health Research, University of Birmingham, Birmingham, England. t.j.h.keeley@bham.ac.uk.
authors.forename: T
authors.initials: T
authors.lastname: Keeley
authors.affiliation: Department of Biostatistics, MRC North West Hub for Trials Methodology Research, University of Liverpool, Liverpool, England.
authors.forename: P
authors.initials: P
authors.lastname: Williamson
authors.affiliation: Midwifery and Social Work, School of Nursing, University of Manchester, Manchester, England.
authors.forename: P
authors.initials: P
authors.lastname: Callery
authors.affiliation: Centre for Patient Reported Outcomes Research, Institute of Applied Health Research, University of Birmingham, Birmingham, England.
authors.forename: L L
authors.initials: LL
authors.lastname: Jones
authors.affiliation: Centre for Patient Reported Outcomes Research, Institute of Applied Health Research, University of Birmingham, Birmingham, England.
authors.forename: J
authors.initials: J
authors.lastname: Mathers
authors.affiliation: Centre for Patient Reported Outcomes Research, Institute of Applied Health Research, University of Birmingham, Birmingham, England.
authors.forename: J
authors.initials: J
authors.lastname: Jones
authors.affiliation: Department of Psychological Sciences and MRC North West Hub for Trials Methodology Research, University of Liverpool, Liverpool, England.
authors.forename: B
authors.initials: B
authors.lastname: Young
authors.affiliation: Centre for Patient Reported Outcomes Research, Institute of Applied Health Research, University of Birmingham, Birmingham, England.
authors.forename: M
authors.initials: M
authors.lastname: Calvert
mesh_terms: D002986:Clinical Trials as Topic / Q000379:methods*; D032921:Consensus; D003697:Delphi Technique; D023381:Endpoint Determination; D006801:Humans; D012107:Research Design; D016896:Treatment Outcome
keywords: Clinical trial; Core outcome sets; Delphi; Methodology; Qualitative research