Abstract
Objectives
The objective of the study was to investigate the application and interpretation of
statistical analyses in a cross-section of systematic reviews (SRs) of therapeutic
interventions, without restriction by journal, clinical condition, or specialty.
Study Design and Setting
We evaluated a random sample of SRs assembled previously, which were indexed in MEDLINE®
during February 2014, focused on a treatment or prevention question, and reported
at least one meta-analysis. The reported statistical methods used in each SR were
extracted from articles and online appendices by one author, with a 20% random sample
extracted in duplicate.
Results
We evaluated 110 SRs; 78/110 (71%) were non-Cochrane SRs and 55/110 (50%) investigated
a pharmacological intervention. The SRs presented a median of 13 (interquartile range:
5–27) meta-analytic effects. When considering the index (primary or first reported)
meta-analysis of each SR, just over half (62/110 [56%]) used the random-effects model,
but few (5/62 [8%]) interpreted the meta-analytic effect correctly (as the average
of the intervention effects across all studies). A statistical test for funnel plot
asymmetry was reported in 17/110 (15%) SRs; however, in only 4/17 (24%) did the test
include the recommended number of at least 10 studies of varying size. Subgroup analyses
accompanied 42/110 (38%) index meta-analyses, but findings were not interpreted with
respect to a test for interaction in 29/42 (69%) cases, and the issue of potential
confounding in the subgroup analyses was not raised in any SR.
Conclusions
There is scope for improvement in the application and interpretation of statistical
analyses in SRs of therapeutic interventions. The involvement of statisticians on
the SR team and establishment of partnerships between researchers with specialist
expertise in SR methods and journal editors may help overcome these shortcomings.
Keywords
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Article info
Publication history
Published online: December 01, 2017
Accepted:
November 26,
2017
Footnotes
Conflict of interest: We have read the journal's policy and the authors of this manuscript have the following competing interests: A.C.T. is an Associate Editor for Journal of Clinical Epidemiology but had no involvement in the peer review process or decision for publication. M.J.P. and J.E.M. are affiliates of Cochrane Australia. M.J.P. is a Co-Convenor of the Cochrane Bias Methods Group. J.E.M. is a Co-Convenor of the Cochrane Statistical Methods Group. A.C.T. is an author of two of the systematic reviews included in this study but was not involved in eligibility assessment or data collection.
Funding: There was no direct funding for this study. M.J.P. is supported by an Australian National Health and Medical Research Council (NHMRC) Early Career Fellowship (1088535). D.G.A. is a National Institute for Health Research Senior Investigator. J.E.M. is supported by an NHMRC Australian Public Health Fellowship (1072366). F.C.L. is supported by the Generalitat Valenciana (PROMETEOII/2015/021). A.C.T. is funded by a Tier 2 Canada Research Chair in Knowledge Synthesis. D.M. is supported in part by a University Research Chair, University of Ottawa. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Data availability: The study protocol, data collection form, and the raw data and statistical analysis code for this study are available on the Open Science Framework: https://osf.io/523bq/.
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