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Abstract
A study was performed to evaluate the extent to which the medical literature may be
misleading as a result of selective publication of randomized clinical trials (RCTs)
with results showing a statistically significant treatment effect. Three hundred eighteen
authors of published trials were asked whether they had participated in any unpublished
RCTs. The 156 respondents reported 271 unpublished and 1041 published trials. Of the
178 completed unpublished RCTs with a trend specified, 26 (14%) favored the new therapy
compared to 423 of 767 (55%) published reports (p less than 0.001). For trials that
were completed but not published, the major reasons for nonpublication were "negative"
results and lack of interest. From the data provided, it appears that nonpublication
was primarily a result of failure to write up and submit the trial results rather
than rejection of submitted manuscripts. The results of this study imply the existence
of a publication bias of importance both to meta-analysis and the interpretation of
statistically significant positive trials.