Association between competing interests and authors' conclusions: epidemiological study of randomised clinical trials published in the BMJ.
OBJECTIVE
To assess the association between competing interests and authors' conclusions in randomised clinical trials.


METHODS
Epidemiological study of randomised clinical trials published in the BMJ from January 1997 to June 2001. Financial competing interests were defined as funding by for profit organisations and other competing interests as personal, academic, or political.


METHODS
159 trials from 12 medical specialties.


METHODS
Authors' conclusions defined as interpretation of extent to which overall results favoured experimental intervention. Conclusions appraised on 6 point scale; higher scores favour experimental intervention.


RESULTS
Authors' conclusions were significantly more positive towards the experimental intervention in trials funded by for profit organisations alone compared with trials without competing interests (mean difference 0.48 (SE 0.13), P=0.014), trials funded by both for profit and non-profit organisations (0.30 (SE 0.10), P=0.003), and trials with other competing interests (0.45 (SE 0.13), P=0.006). Other competing interests and funding from both for profit and non-profit organisations were not significantly associated with authors' conclusions. The association between financial competing interests and authors' conclusions was not explained by methodological quality, statistical power, type of experimental intervention (pharmacological or non-pharmacological), type of control intervention (for example, placebo or active drug), or medical specialty.


CONCLUSIONS
Authors' conclusions in randomised clinical trials significantly favoured experimental interventions if financial competing interests were declared. Other competing interests were not significantly associated with authors' conclusions.
Kjaergard
Lise L
LL
Cochrane Hepatobiliary Group, Copenhagen Trial Unit, Centre for Clinical Intervention Research, Copenhagen University Hospital, Department 7102, H:S Rigshospitalet, DK-2100 Copenhagen, Denmark. Kjaergard@ctu.rh.dk
Als-Nielsen
Bodil
B
D000704:Analysis of Variance; D016265:Conflict of Interest; D003627:Data Interpretation, Statistical; D006801:Humans; D010506:Periodicals as Topic; D016032:Randomized Controlled Trials as Topic / Q000592:standards*; D012109:Research Support as Topic
Biomedical and Behavioral Research; Empirical Approach