title: Development of a combined database for meta-epidemiological research.
abstract: Collections of meta-analyses assembled in meta-epidemiological studies are used to study associations of trial characteristics with intervention effect estimates. However, methods and findings are not consistent across studies. To combine data from 10 meta-epidemiological studies into a single database, and derive a harmonized dataset without overlap between meta-analyses. The database design allowed trials to be contained in different meta-analyses, multiple meta-analyses in systematic reviews, overlapping meta-analyses between systematic reviews, and multiple references to the same trial or review. Unique identifiers were assigned to each reference and used to identify duplicate trials. Sets of meta-analyses with overlapping trials were identified and duplicates removed. Overlapping trials were used to examine agreement between assessments of trial characteristics. The combined database contained 427 reviews, 454 meta-analyses and 4874 trial results. Of these, 258 meta-analyses were unique, while for 196 at least one trial overlapped with another meta-analysis. Median kappa statistics for reliability of assessments were 0.60 for sequence generation, 0.58 for allocation concealment and 0.87 for blinding. Based on inspection of sets of overlapping meta-analyses, 91 meta-analyses containing 1344 trial results were removed. Additionally, 24 duplicated trial results were removed from 16 meta-analyses, to derive a final database containing 363 meta-analyses and 3477 unique trial results. The final database will be used to examine the combined evidence on sources of bias in randomized controlled trials. The strategy used to remove overlap between meta-analyses may be of use for future empirical research. Copyright © 2010 John Wiley & Sons, Ltd.
authors.affiliation: School of Social and Community Medicine, University of Bristol, Bristol, U.K.
authors.forename: Jelena
authors.initials: J
authors.lastname: Savović
authors.affiliation: Centre for Infections, Health Protection Agency, Colindale, U.K.
authors.forename: Ross J
authors.initials: RJ
authors.lastname: Harris
authors.affiliation: School Food Trust, Sheffield, U.K.
authors.forename: Lesley
authors.initials: L
authors.lastname: Wood
authors.affiliation: School of Social and Community Medicine, University of Bristol, Bristol, U.K.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Beynon
authors.affiliation: Centre for Statistics in Medicine, University of Oxford, Wolfson College, Oxford, U.K.
authors.forename: Doug
authors.initials: D
authors.lastname: Altman
authors.affiliation: Copenhagen Trial Unit, Centre for Clinical Intervention Research and Department of Paediatrics, Copenhagen University Hospital, Copenhagen, Denmark.
authors.forename: Bodil
authors.initials: B
authors.lastname: Als-Nielsen
authors.affiliation: Center for Clinical Evidence Synthesis, Tufts Clinical and Translational Science Institute, Tufts Medical Center, Boston, MA, U.S.A.
authors.forename: Ethan M
authors.initials: EM
authors.lastname: Balk
authors.affiliation: Public Health Epidemiology and Biostatistics, School of Health and Population Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, U.K.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Deeks
authors.affiliation: Department of Internal Medicine, Copenhagen University Hospital, Gentofte, Denmark.
authors.forename: Lise Lotte
authors.initials: LL
authors.lastname: Gluud
authors.affiliation: Copenhagen Trial Unit, Centre for Clinical Intervention Research, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark.
authors.forename: Christian
authors.initials: C
authors.lastname: Gluud
authors.affiliation: Department of Hygiene and Epidemiology, University of Ioannina School of Medicine, Ioannina, Greece.|Department of Medicine, Tufts University School of Medicine, Boston, U.S.A.|Department of Epidemiology, Harvard School of Public Health, Boston, U.S.A.
authors.forename: John P A
authors.initials: JP
authors.lastname: Ioannidis
authors.affiliation: Division of Clinical Epidemiology and Biostatistics, Institute of Social and Preventive Medicine, University of Bern, Bern, Switzerland.|CTU Bern, Bern University Hospital, Bern, Switzerland.
authors.forename: Peter
authors.initials: P
authors.lastname: Jűni
authors.affiliation: Ottawa Methods Centre, Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa, Canada.
authors.forename: David
authors.initials: D
authors.lastname: Moher
authors.affiliation: The Nordic Cochrane Centre, Rigshospitalet, Copenhagen, Denmark.
authors.forename: Julie
authors.initials: J
authors.lastname: Pildal
authors.affiliation: Quantitative Sciences, Family Health International, Research Triangle Park, Durham, NC 27709, U.S.A.
authors.forename: Kenneth F
authors.initials: KF
authors.lastname: Schulz
authors.affiliation: School of Social and Community Medicine, University of Bristol, Bristol, U.K.. jonathan.sterne@bristol.ac.uk.
authors.forename: Jonathan A C
authors.initials: JA
authors.lastname: Sterne
keywords: bias; data management; meta‐analysis; meta‐epidemiology; systematic reviews