title: How individual participant data meta-analyses have influenced trial design, conduct, and analysis.
abstract: OBJECTIVE
  To demonstrate how individual participant data (IPD) meta-analyses have impacted directly on the design and conduct of trials and highlight other advantages IPD might offer.
  
  
  METHODS
  Potential examples of the impact of IPD meta-analyses on trials were identified at an international workshop, attended by individuals with experience in the conduct of IPD meta-analyses and knowledge of trials in their respective clinical areas. Experts in the field who did not attend were asked to provide any further examples. We then examined relevant trial protocols, publications, and Web sites to verify the impacts of the IPD meta-analyses. A subgroup of workshop attendees sought further examples and identified other aspects of trial design and conduct that may inform IPD meta-analyses.
  
  
  RESULTS
  We identified 52 examples of IPD meta-analyses thought to have had a direct impact on the design or conduct of trials. After screening relevant trial protocols and publications, we identified 28 instances where IPD meta-analyses had clearly impacted on trials. They have influenced the selection of comparators and participants, sample size calculations, analysis and interpretation of subsequent trials, and the conduct and analysis of ongoing trials, sometimes in ways that would not possible with systematic reviews of aggregate data. We identified additional potential ways that IPD meta-analyses could be used to influence trials.
  
  
  CONCLUSIONS
  IPD meta-analysis could be better used to inform the design, conduct, analysis, and interpretation of trials.
authors.affiliation: MRC Clinical Trials Unit at UCL, Aviation House, 125 Kingsway, London WC2B 6NH, UK. Electronic address: jayne.tierney@ucl.ac.uk.
authors.forename: Jayne F
authors.initials: JF
authors.lastname: Tierney
authors.affiliation: LNCC plateforme de méta-analyse en oncologie, Service de Biostatistique et d'Epidemiologie, Gustave-Roussy, Villejuif, France.
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Pignon
authors.affiliation: Université Claude Bernard Lyon 1/Université de Lyon, 69365 Lyon Cedex 07, Lyon, France; Service de Pharmacologie Clinique, Hospices Civils de Lyon, Bron cedex, France.
authors.forename: Francois
authors.initials: F
authors.lastname: Gueffyier
authors.affiliation: All-Ireland Hub for Trials Methodology Research, Queen's University Belfast, University Road, Belfast BT7 1NN, Northern Ireland, UK.
authors.forename: Mike
authors.initials: M
authors.lastname: Clarke
authors.affiliation: NHMRC Clinical Trials Centre, ABN 15 211 513 464, Locked Bag 77, Camperdown, NSW 1450 Australia.
authors.forename: Lisa
authors.initials: L
authors.lastname: Askie
authors.affiliation: MRC Clinical Trials Unit at UCL, Aviation House, 125 Kingsway, London WC2B 6NH, UK.
authors.forename: Claire L
authors.initials: CL
authors.lastname: Vale
authors.affiliation: MRC Clinical Trials Unit at UCL, Aviation House, 125 Kingsway, London WC2B 6NH, UK.
authors.forename: Sarah
authors.initials: S
authors.lastname: Burdett
mesh_terms: D002986:Clinical Trials as Topic / Q000379:methods*; D006801:Humans; D015201:Meta-Analysis as Topic; D012107:Research Design; D035842:Research Subjects; D013223:Statistics as Topic
keywords: Individual participant data (IPD); Meta-analysis; Systematic review; Trial analysis; Trial conduct; Trial design