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Financial ties and concordance between results and conclusions in meta-analyses: retrospective cohort study

BMJ 2007; 335 doi: (Published 06 December 2007) Cite this as: BMJ 2007;335:1202
  1. Veronica Yank, clinical instructor1,
  2. Drummond Rennie, professor2,
  3. Lisa A Bero, professor3
  1. 1Stanford University, Stanford Medical Group, Stanford, CA 94305-5765, USA
  2. 2University of California, San Francisco
  3. 3Clinical Pharmacy and Institute for Health Policy Studies, University of California, San Francisco
  1. Correspondence to: V Yank
  • Accepted 21 September 2007


Objective To determine whether financial ties to one drug company are associated with favourable results or conclusions in meta-analyses on antihypertensive drugs.

Design Retrospective cohort study.

Setting Meta-analyses published up to December 2004 that were not duplicates and evaluated the effects of antihypertensive drugs compared with any comparator on clinical end points in adults. Financial ties were categorised as one drug company compared with all others.

Main outcome measures The main outcomes were the results and conclusions of meta-analyses, with both outcomes separately categorised as being favourable or not favourable towards the study drug. We also collected data on characteristics of meta-analyses that the literature suggested might be associated with favourable results or conclusions.

Results 124 meta-analyses were included in the study, 49 (40%) of which had financial ties to one drug company. On univariate logistic regression analyses, meta-analyses of better methodological quality were more likely to have favourable results (odds ratio 1.16, 95% confidence interval 1.07 to 1.27). Although financial ties to one drug company were not associated with favourable results, such ties constituted the only characteristic significantly associated with favourable conclusions (4.09, 1.30 to 12.83). When controlling for other characteristics of meta-analyses in multiple logistic regression analyses, meta-analyses that had financial ties to one drug company remained more likely to report favourable conclusions (5.11, 1.54 to 16.92).

Conclusion Meta-analyses on antihypertensive drugs and with financial ties to one drug company are not associated with favourable results but are associated with favourable conclusions.


  • We thank Alan Bostrom (University of California, San Francisco), the biostatistician for the study, who carried out the statistical analyses and provided input on the interpretation of these analyses.

  • Contributors: VY refined the idea for the study; designed and coordinated the pilot study, and collected, analysed, and interpreted its data; designed all parts of the current study; coordinated the study; carried out the literature and manual searches; evaluated all potential meta-analyses for inclusion; collected data from all included meta-analyses; analysed the data along with the biostatistician; interpreted the data; and wrote the paper. She is guarantor for the paper. DR had the initial idea for the study; collected data in the pilot study; provided input on the design, data collection, analyses, and interpretation of the study; and reviewed and provided substantive feedback on the paper. LAB provided input on the design, data collection, analyses, and interpretation of the study; gave special input on the data extraction tool; collected data for the pilot study and a subset of meta-analyses in the current study; and reviewed and provided substantive feedback on the paper.

  • Funding: The study was funded in part by the Eugene Garfield Foundation. VY received support from a dean’s quarterly research grant (University of California, San Francisco) and from the internal medicine residency program (University of Washington, Seattle). LAB receives support from the California tobacco related disease research program (grant No 13RT-0108H).

  • Competing interests: None declared.

  • Ethical approval: Not required.

  • Accepted 21 September 2007
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