Drug Trials Give Best Results to Sponsors
Clinical trials that compare two similar drugs are significantly more likely
to favour the one made by the company that pays for the work, according to a study
that sheds new light on bias in medical research.
An analysis of almost
200 published comparison trials indicated that when the findings show one drug
to be superior, the study is about 20 times more likely to have been funded by
The link between the funding and the outcome is even
stronger when authors discuss the implications of their results: papers that include
positive interpretations are about 35 times more likely to have been paid for
by the drugs maker.
The work, by a team led by Lisa Bero, Professor of
Clinical Pharmacy at the University of California, San Francisco, raises fresh
concern about the influence of pharmaceutical companies over research. Peer-reviewed
medical literature is one of the sources used by funding bodies such as the National
Institute for Health and Clinical Excellence and insurers when deciding which
drugs should be made available.
"Many people are concerned about the
growing proportion of drug trials funded by the drugs manufacturers, Professor
Bero said."If drug-trial outcomes are largely determined by who pays for the trial,
we don't really know what the best drug is.
The research, published in Public
Library of Science Medicine, examined studies of statins. It does not suggest
that scientists funded by the drug industry manipulate data, but points to subtle
ways in which they can be influenced, such as by comparing a normal dose with
a low dose of a rival drug.
Source; M. Henderson; The Times, June 2007
Factors Associated with Findings of Published
Trials of Drug, Drug Comparisons: Why Some Statins Appear More Efficacious than
Lisa Bero1*, Fieke Oostvogel2, Peter Bacchetti3, Kirby Lee4 1
Pharmacy and Health Policy, University of California, San Francisco, California,
United States of America, 2 Department of Mathematics, University of Leiden, The
Netherlands, 3 Department of Epidemiology and Biostatistics, University of California,
San Francisco, California, United States of America, 4 Department of Clinical
Pharmacy, University of California, San Francisco, California, United States of
Published pharmaceutical industry sponsored trials
are more likely than non-industry-sponsored trials to report results and conclusions
that favor drug over placebo. Little is known about potential biases in drug,
drug comparisons. This study examined associations between research funding source,
study design characteristics aimed at reducing bias, and other factors that potentially
influence results and conclusions in randomized controlled trials (RCTs) of statin
Methods and Findings
This is a cross-sectional
study of 192 published RCTs comparing a statin drug to another statin drug or
non-statin drug. Data on concealment of allocation, selection bias, blinding,
sample size, disclosed funding source, financial ties of authors, results for
primary outcomes, and author conclusions were extracted by two coders (weighted
kappa 0.80 to 0.97). Univariate and multivariate logistic regression identified
associations between independent variables and favorable results and conclusions.
Of the RCTs, 50% (95/192) were funded by industry, and 37% (70/192) did not disclose
any funding source. Looking at the totality of available evidence, we found that
almost all studies (98%, 189/192) used only surrogate outcome measures. Moreover,
study design weaknesses common to published statin drug comparisons included inadequate
blinding, lack of concealment of allocation, poor follow-up, and lack of intention-to-treat
analyses. In multivariate analysis of the full sample, trials with adequate blinding
were less likely to report results favoring the test drug, and sample size was
associated with favorable conclusions when controlling for other factors. In multivariate
analysis of industry-funded RCTs, funding from the test drug company was associated
with results (odds ratio = 20.16 [95% confidence interval 4.37 92.980], p<0.001)
and conclusions (odds ratio = 34.55 [95% confidence interval 7.09 168.4], p <
0.001) that favor the test drug when controlling for other factors. Studies with
adequate blinding were less likely to report statistically significant results
favoring the test drug.
RCTs of head-to-head
comparisons of statins with other drugs are more likely to report results and
conclusions favoring the sponsor's product compared to the comparator drug. This
bias in drug/drug comparison trials should be considered when making decisions
regarding drug choice.
Funding: This research was supported by the
California Tobacco-Related Disease Research Program Grant 13RT-0108 (principal
investigator, L. A. Bero). The funders had no role in study design, data collection
and analysis, decision to publish, or preparation of the manuscript.
Interests: The authors have declared that no competing interests exist.
Editor: Alessandro Liberati, Italian Cochrane Centre, Italy Citation: Bero
L, Oostvogel F, Bacchetti P, Lee K (2007) Factors Associated with Findings of
Published Trials of Drug/ Drug Comparisons: Why Some Statins Appear More Efficacious
than Others. PLoS Med 4(6): e184 doi:10.1371/journal.pmed.0040184
September 4, 2006; Accepted: April 2, 2007; Published: June 5, 2007
Copyright: © 2007 Bero et al. This is an open-access article distributed
under the terms of the Creative Commons Attribution License, which permits unrestricted
use, distribution, and reproduction in any medium, provided the original author
and source are credited. Abbreviations: CI, confidence interval; OR, odds ratio;
RCT, randomized controlled trial * To whom correspondence should be addressed.
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