To estimate the frequency with which results of large randomized clinical trials registered with ClinicalTrials.gov are not available to the public.
Cross sectional analysis
Trials with at least 500 participants that were prospectively registered with ClinicalTrials.gov and completed prior to January 2009.
PubMed, Google Scholar, and Embase were searched to identify published manuscripts containing trial results. The final literature search occurred in November 2012. Registry entries for unpublished trials were reviewed to determine whether results for these studies were available in the ClinicalTrials.gov results database.
对PubMed, Google Scholar, and Embase网站进行了全面搜查来辨别那些含有试验结果的已发表原稿。最后的文献检索发生在2012年11月。对未发表试验的注册表项进行审查以确定是否这些研究的结果能在ClinicalTrials.gov的结果数据库中查找到。
Main outcome measures
The frequency of non-publication of trial results and, among unpublished studies, the frequency with which results are unavailable in the ClinicalTrials.gov database.
Of 585 registered trials, 171 (29%) remained unpublished. These 171 unpublished trials had an estimated total enrollment of 299 763 study participants. The median time between study completion and the final literature search was 60 months for unpublished trials. Non-publication was more common among trials that received industry funding (150/468, 32%) than those that did not (21/117, 18%), P=0.003. Of the 171 unpublished trials, 133 (78%) had no results available in ClinicalTrials.gov.
585项已注册试验中的171 项（ 29 ％ ）仍然未公布。这171项未发表的试验估计总共招募了299 763名研究参与者。未发表试验从研究完成到最后文献可检索之间经历的平均时间为60个月。那些获得工业资助的试验（150/ 468 32 ％）比起那些未获得资助的试验（（21 /117， 18 ％ ），P = 0.003）更易不公开。171项未公开试验中的133 项（ 78 ％ ）在ClinicalTrials.gov中无法查询到结果。
Among this group of large clinical trials, non-publication of results was common and the availability of results in the ClinicalTrials.gov database was limited. A substantial number of study participants were exposed to the risks of trial participation without the societal benefits that accompany the dissemination of trial results.