Publication and non-publication of clinical trials: longitudinal study of applications submitted to a research ethics committee.
BACKGROUND
Not all clinical trials are published, which may distort the evidence that is available in the literature. We studied the publication rate of a cohort of clinical trials and identified factors associated with publication and nonpublication of results.


METHODS
We analysed the protocols of randomized clinical trials of drug interventions submitted to the research ethics committee of University Hospital (Inselspital) Bern, Switzerland from 1988 to 1998. We identified full articles published up to 2006 by searching the Cochrane CENTRAL database (issue 02/2006) and by contacting investigators. We analyzed factors associated with the publication of trials using descriptive statistics and logistic regression models.


RESULTS
451 study protocols and 375 corresponding articles were analyzed. 233 protocols resulted in at least one publication, a publication rate of 52%. A total of 366 (81%) trials were commercially funded, 47 (10%) had non-commercial funding. 346 trials (77%) were multi-centre studies and 272 of these (79%) were international collaborations. In the adjusted logistic regression model non-commercial funding (Odds Ratio [OR] 2.42, 95% CI 1.14-5.17), multi-centre status (OR 2.09, 95% CI 1.03-4.24), international collaboration (OR 1.87, 95% CI 0.99-3.55) and a sample size above the median of 236 participants (OR 2.04, 95% CI 1.23-3.39) were associated with full publication.


CONCLUSIONS
In this cohort of applications to an ethics committee in Switzerland, only about half of clinical drug trials were published. Large multi-centre trials with non-commercial funding were more likely to be published than other trials, but most trials were funded by industry.
von Elm
Erik
E
Institute of Social and Preventive Medicine (ISPM), University of Bern, Bern, Switzerland.
Röllin
Alexandra
A
Blümle
Anette
A
Huwiler
Karin
K
Witschi
Mark
M
Egger
Matthias
M
D015982:Bias; D002985:Clinical Protocols; D003625:Data Collection; D019992:Databases as Topic; D015195:Drug Design; D028744:Ethics Committees, Research; D019317:Evidence-Based Medicine; D006801:Humans; D018156:Journalism, Medical / Q000592:standards; D008137:Longitudinal Studies; D010506:Periodicals as Topic; D016032:Randomized Controlled Trials as Topic; D012107:Research Design; D012109:Research Support as Topic; D011795:Surveys and Questionnaires