- Joel Lexchin, associate professor ()1,
- Lisa A Bero, professor2,
- Benjamin Djulbegovic, associate professor3,
- Otavio Clark, chief of clinical oncology section4
- 1 School of Health Policy and Management, York University, Toronto, ON, Canada M3J 1P3
- 2 Department of Clinical Pharmacy and Institute for Health Policy Studies, University of California at San Francisco, San Francisco, CA 94118, USA
- 3 Interdisciplinary Oncology Program, H Lee Moffitt Cancer Center and Research Institute, University of South Florida, Tampa, FL 33612, USA
- 4 Instituto do Radium de Campinas, 13075–460 Campinas-SP, Brazil
- Correspondence to: J Lexchin
- Accepted 15 April 2003
Objective To investigate whether funding of drug studies by the pharmaceutical industry is associated with outcomes that are favourable to the funder and whether the methods of trials funded by pharmaceutical companies differ from the methods in trials with other sources of support.
Methods Medline (January 1966 to December 2002) and Embase (January 1980 to December 2002) searches were supplemented with material identified in the references and in the authors' personal files. Data were independently abstracted by three of the authors and disagreements were resolved by consensus.
Results 30 studies were included. Research funded by drug companies was less likely to be published than research funded by other sources. Studies sponsored by pharmaceutical companies were more likely to have outcomes favouring the sponsor than were studies with other sponsors (odds ratio 4.05; 95% confidence interval 2.98 to 5.51; 18 comparisons). None of the 13 studies that analysed methods reported that studies funded by industry was of poorer quality.
Conclusion Systematic bias favours products which are made by the company funding the research. Explanations include the selection of an inappropriate comparator to the product being investigated and publication bias.
We thank Jiri Chard, David Liebeskind, Paula Rochon, and José Sacristan for additional information and data about their studies.
Contributors: JL conceived and planned the study, did the Medline search, extracted the data, and wrote the paper. LAB planned the study, extracted the data, and wrote the paper. BD planned the study, checked the data extraction process, and wrote the paper. OC extracted the data and wrote the paper. JL is guarantor.
Funding No additional funding.
Competing interests BD has been funded by several pharmaceutical companies to perform research and has received speaking honorariums.
- Accepted 15 April 2003