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J Clin Epidemiol. 2014 Aug;67(8):897-903. doi: 10.1016/j.jclinepi.2014.03.003. Epub 2014 Apr 29.

In meta-analyses of proportion studies, funnel plots were found to be an inaccurate method of assessing publication bias.

Author information

1
ST5 Vascular Surgery, Leicester Royal Infirmary, Leicester, LE1 5WW, UK. Electronic address: jhunter@doctors.net.uk.
2
ST3 General Surgery, University Hospitals Coventry and Warwickshire NHS Trust, Infirmary square, UK.
3
Department of Health Sciences, University of Leicester, University Road, Leicester, LE1 7RD, UK.
4
Department of Cardiovascular Sciences, University of Leicester, University Road, Leicester, LE1 7RD, UK.
5
Department of Cardiovascular Sciences, and the NIHR Leicester Cardiovascular Biomedical Research Unit, University of Leicester, University Road, Leicester, LE1 7RD, UK.

Abstract

OBJECTIVE:

To assess the utility of funnel plots in assessing publication bias (PB) in meta-analyses of proportion studies.

STUDY DESIGN AND SETTING:

Meta-analysis simulation study and meta-analysis of published literature reporting peri-operative mortality after abdominal aortic aneurysm (AAA) repair. Data for the simulation study were stochastically generated. A literature search of Medline and Embase was performed to identify studies for inclusion in the published literature meta-analyses.

RESULTS:

The simulation study demonstrated that conventionally constructed funnel plots (log odds vs. 1/standard error [1/SE]) for extreme proportional outcomes were asymmetric despite no PB. Alternative funnel plots constructed using study size rather than 1/SE showed no asymmetry for extreme proportional outcomes. When used in meta-analyses of the mortality of AAA repair, these alternative funnel plots highlighted the possibility for conventional funnel plots to demonstrate asymmetry when there was no evidence of PB.

CONCLUSION:

Conventional funnel plots used to assess for potential PB in meta-analyses are inaccurate for meta-analyses of proportion studies with low proportion outcomes. Funnel plots of study size against log odds may be a more accurate way of assessing for PB in these studies.

KEYWORDS:

Abdominal aortic aneurysm; Funnel plot; Meta-analysis; Peri-operative mortality; Proportional outcomes; Publication bias

PMID:
24794697
DOI:
10.1016/j.jclinepi.2014.03.003
[Indexed for MEDLINE]

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