title: Publication bias is underreported in systematic reviews published in high-impact-factor journals: metaepidemiologic study.
abstract: OBJECTIVE
  To examine how often a significant publication bias (PB) existed when the assessment of PB was not reported in systematic reviews.
  
  
  METHODS
  All systematic reviews with meta-analyses of interventions and risk/prognostic factors published in the general medical journals with the top 10 impact factors in 2011 and 2012 were included. The results regarding PB were extracted. When the assessment of PB was not reported, we examined the presence of PB using the Egger test and contour-enhanced funnel plot and the impact of unreported PB by regression-based method.
  
  
  RESULTS
  Among all the identified 116 reviews, the assessment of PB was not reported in 36 reviews (31.0%), particularly in reviews without a comprehensive literature search. Of these 36 reviews, seven (19.4%) were found to have a significant PB. The original pooled results may have been overestimated by a median of 50.9% if corrected for PB. Among the 28 reviews with PB including both reviews that did or did not report the assessment of PB, seven reviews (25.0%) did not report the presence of PB.
  
  
  CONCLUSIONS
  Significant PB was underreported in systematic reviews published in high-impact-factor journals (eg, 19.4% of those that did not report assessment of PB had significant PB). Readers of systematic reviews should not assume that PB does not exist when not reported whereas researchers should report the results of assessments for PB.
authors.affiliation: Department of Health Promotion and Human Behavior, Kyoto University Graduate School of Medicine/School of Public Health, Yoshida Konoe-cho, Sakyo-ku, Kyoto 606-8501 Japan. Electronic address: aonishi@med.kobe-u.ac.jp.
authors.forename: Akira
authors.initials: A
authors.lastname: Onishi
authors.affiliation: Department of Health Promotion and Human Behavior, Kyoto University Graduate School of Medicine/School of Public Health, Yoshida Konoe-cho, Sakyo-ku, Kyoto 606-8501 Japan.
authors.forename: Toshi A
authors.initials: TA
authors.lastname: Furukawa
mesh_terms: D006801:Humans; D055811:Journal Impact Factor; D015201:Meta-Analysis as Topic; D017594:Publication Bias / Q000706:statistics & numerical data*; D012196:Review Literature as Topic
keywords: Funnel plot symmetry; Impact factor; Meta-analysis; Publication bias; Small-study effects; Systematic review