title: Core Outcome Set-STAndards for Reporting: The COS-STAR Statement.
abstract: BACKGROUND
  Core outcome sets (COS) can enhance the relevance of research by ensuring that outcomes of importance to health service users and other people making choices about health care in a particular topic area are measured routinely. Over 200 COS to date have been developed, but the clarity of these reports is suboptimal. COS studies will not achieve their goal if reports of COS are not complete and transparent.
  
  
  RESULTS
  In recognition of these issues, an international group that included experienced COS developers, methodologists, journal editors, potential users of COS (clinical trialists, systematic reviewers, and clinical guideline developers), and patient representatives developed the Core Outcome Set-STAndards for Reporting (COS-STAR) Statement as a reporting guideline for COS studies. The developmental process consisted of an initial reporting item generation stage and a two-round Delphi survey involving nearly 200 participants representing key stakeholder groups, followed by a consensus meeting. The COS-STAR Statement consists of a checklist of 18 items considered essential for transparent and complete reporting in all COS studies. The checklist items focus on the introduction, methods, results, and discussion section of a manuscript describing the development of a particular COS. A limitation of the COS-STAR Statement is that it was developed without representative views of low- and middle-income countries. COS have equal relevance to studies conducted in these areas, and, subsequently, this guideline may need to evolve over time to encompass any additional challenges from developing COS in these areas.
  
  
  CONCLUSIONS
  With many ongoing COS studies underway, the COS-STAR Statement should be a helpful resource to improve the reporting of COS studies for the benefit of all COS users.
authors.affiliation: MRC North West Hub for Trials Methodology Research, Department of Biostatistics, University of Liverpool, Liverpool, United Kingdom.
authors.forename: Jamie J
authors.initials: JJ
authors.lastname: Kirkham
authors.affiliation: MRC North West Hub for Trials Methodology Research, Department of Biostatistics, University of Liverpool, Liverpool, United Kingdom.
authors.forename: Sarah
authors.initials: S
authors.lastname: Gorst
authors.affiliation: Centre for Statistics in Medicine, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, United Kingdom.
authors.forename: Douglas G
authors.initials: DG
authors.lastname: Altman
authors.affiliation: MRC ConDuCT II Hub for Trials Methodology Research, School of Social and Community Medicine, University of Bristol, Bristol, United Kingdom.
authors.forename: Jane M
authors.initials: JM
authors.lastname: Blazeby
authors.affiliation: Northern Ireland Hub for Trials Methodology Research, Centre for Public Health, Queen's University Belfast, Belfast, United Kingdom.
authors.forename: Mike
authors.initials: M
authors.lastname: Clarke
authors.affiliation: National University of Ireland Galway and HRB Trials Methodology Research Network, Ireland.
authors.forename: Declan
authors.initials: D
authors.lastname: Devane
authors.affiliation: MRC North West Hub for Trials Methodology Research, Department of Biostatistics, University of Liverpool, Liverpool, United Kingdom.
authors.forename: Elizabeth
authors.identifier: http://orcid.org/0000-0002-3848-0113
authors.initials: E
authors.lastname: Gargon
authors.affiliation: Ottawa Methods Centre, Ottawa Hospital Research Institute, Ottawa, Canada.
authors.forename: David
authors.initials: D
authors.lastname: Moher
authors.affiliation: Center for Evidence-Based Healthcare, Medizinische Fakultät, Technische Universität Dresden, Dresden, Germany.
authors.forename: Jochen
authors.initials: J
authors.lastname: Schmitt
authors.affiliation: Institute of Population Health, University of Ottawa, Ottawa, Canada.
authors.forename: Peter
authors.initials: P
authors.lastname: Tugwell
authors.affiliation: Center for Medical Technology Policy, Baltimore, Maryland, United States of America.
authors.forename: Sean
authors.initials: S
authors.lastname: Tunis
authors.affiliation: MRC North West Hub for Trials Methodology Research, Department of Biostatistics, University of Liverpool, Liverpool, United Kingdom.
authors.forename: Paula R
authors.initials: PR
authors.lastname: Williamson
mesh_terms: D035843:Biomedical Research; D057189:Checklist; D003245:Consensus Statements as Topic; D017408:Guidelines as Topic; D017063:Outcome Assessment, Health Care / Q000379:methods / Q000592:standards*; D012196:Review Literature as Topic