title: Outcome selection bias in meta-analysis.
abstract: Publication bias has been previously identified as a threat to the validity of a meta-analysis. Recently, new evidence has documented an additional threat to validity, the selective reporting of trial outcomes within published studies. Several diseases have several possible measures of outcome. Some articles might report only a selection of those outcomes, perhaps those with statistically significant results. In this article, we review this problem while addressing the questions: what is within-study selective reporting? how common is it? why is it done? how can it mislead? how can it be detected?, and finally, what is the solution? We recommend that both publication bias and selective reporting should be routinely investigated in systematic reviews.
authors.affiliation: Centre for Medical Statistics and Health Evaluation, Shelley's Cottage, Brownlow Street, University of Liverpool, Liverpool L69 3GS, UK. prw@liv.ac.uk
authors.forename: P R
authors.initials: PR
authors.lastname: Williamson
authors.forename: C
authors.initials: C
authors.lastname: Gamble
authors.forename: D G
authors.initials: DG
authors.lastname: Altman
authors.forename: J L
authors.initials: JL
authors.lastname: Hutton
mesh_terms: D015982:Bias; D002986:Clinical Trials as Topic; D006801:Humans; D015201:Meta-Analysis as Topic; D017063:Outcome Assessment, Health Care / Q000706:statistics & numerical data*; D011642:Publications; D015203:Reproducibility of Results; D006113:United Kingdom