Evidence b(i)ased medicine--selective reporting from studies sponsored by pharmaceutical industry: review of studies in new drug applications

Abstract

Objectives: To investigate the relative impact on publication bias caused by multiple publication, selective publication, and selective reporting in studies sponsored by pharmaceutical companies.

Design: 42 placebo controlled studies of five selective serotonin reuptake inhibitors submitted to the Swedish drug regulatory authority as a basis for marketing approval for treating major depression were compared with the studies actually published (between 1983 and 1999).

Results: Multiple publication: 21 studies contributed to at least two publications each, and three studies contributed to five publications. Selective publication: studies showing significant effects of drug were published as stand alone publications more often than studies with non-significant results. Selective reporting: many publications ignored the results of intention to treat analyses and reported the more favourable per protocol analyses only.

Conclusions: The degree of multiple publication, selective publication, and selective reporting differed between products. Thus, any attempt to recommend a specific selective serotonin reuptake inhibitor from the publicly available data only is likely to be based on biased evidence.

Fig 1

Publication pattern for studies of the five selective serotonin reuptake inhibitors approved in Sweden between 1989 and 1994 for treating major depression

Fig 2

Difference in estimated size of treatment effect (% response to drug minus response to placebo) from published studies and estimate from intention to treat analysis of submitted studies plotted against total sample size.

Fig 3

Differences (95% confidence intervals) in response rate (% response to drug minus response to placebo). Results from pooled analyses of all submitted studies, correct selection of published studies (duplicates excluded), and plausible selection of published studies (including probably undetectable duplicates)