Grey literature in systematic reviews: a cross-sectional study of the contribution of non-English reports, unpublished studies and dissertations to the results of meta-analyses in child-relevant reviews

Ref ID 684
First Author L. Hartling
Journal BMC MEDICAL RESEARCH METHODOLOGY
Year Of Publishing 2017
URL https://dx.doi.org/10.1186/s12874-017-0347-z
Keywords • Cochrane
• Grey literature
• Paediatrics
• Language
Problem(s) • Language restriction
• Grey literature excluded
Article Type Empirical
Article Subtype Meta-epidemiological analysis
First Author Country Canada
Aim To assess the searches for and contribution of non-English reports, unpublished studies, and dissertations and their impact on results of meta-analyses from child-relevant Cochrane registered systematic reviews.
Level of Investigation Descriptive
Summary of Findings Whilst the majority of included reviews searched for non-English studies, only 12% of reviews included non-English studies. Most reviews also searched for unpublished studies but only 6% included unpublished studies.
Number of systematic reviews included 129
Number of eligible systematic reviews assessed 1345
Treatment impacted Yes
Treatment impacted description Inclusion of non-English, unpublished studies and dissertation was examined in the meta-analyses of included reviews to study the impact to the effect size.
Interpretation impacted Yes
Interpretation impacted description In a minority of cases, inclusion of non-English studies, unpublished studies or dissertations caused large changes to the effect size.