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05 Mart 2013

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Research Letters |

Time to Publication Among Completed Clinical Trials ONLINE FIRST

Joseph S. Ross, MD, MHS; Marian Mocanu, MD; Julianna F. Lampropulos, MD; Tony Tse, PhD; Harlan M. Krumholz, MD, SM

JAMA Intern Med. 2013;():1-3. doi:10.1001/jamainternmed.2013.136.


Prior studies have shown that 25% to 50% of clinical trials are never published.14 However, among those published, we know little about the length of time required for publication in the peer-reviewed biomedical literature after study completion. Ioannidis5 previously demonstrated that a sample of randomized phase 2 and 3 trials conducted between 1986 and 1996 required nearly 2.5 years for publication, while our more recent study of National Institutes of Health (NIH)-funded trials found that the average time to publication was almost 2 years.4 We sought to determine time to publication for a recent and representative sample of trials published in 2009.



We obtained additional information through the National Library of Medicine, using the ClinicalTrials.gov identifier, including data elements reporting lead sponsor, study design, and condition studied (Table). We obtained journal impact factors from Web of Knowledge (Thomson Reuters). We used Kruskal-Wallis tests to compare median times to publication between trial characteristic categories using a type I error rate of 0.003 to account for multiple comparisons (n = 16). Statistical analysis was performed using JMP 7.0.1 software (SAS Institute Inc).

Table. Time to Publication Among Completed Clinical Trials Registered in ClinicalTrials.gov and Published in the Biomedical Literature (Cited in MEDLINE), Stratified by Trial Characteristics



Median time to publication was 21 months, with an interquartile range of 13 to 32 months (eFigure) and modest differences across types of trials (Table). For instance, median time to publication was longer among trials funded by industry compared with trials funded by government and nonprofit organizations (24 vs 20 months; P < .001), but was shorter among trials enrolling 1000 subjects or more compared with trials enrolling 100 subjects or fewer and trials enrolling between 100 and 1000 subjects (18, 20, and 23 months, respectively; P < .001) and was shorter among trials published in journals with an impact factor greater than 10 compared with trials published in journals with an impact factor less than 10 (17 vs 23 months; P < .001).


We found, on average, that nearly 2 years had passed between completion and publication of clinical trials, across all trial funders. Moreover, given that our study was necessarily limited to examining time to publication among completed trials that were eventually published, this estimate is conservative. First, we studied trials registered in and linked to ClinicalTrials.gov, a select group of studies. Because of policies in place as of 2005, many may have been registered to ensure compliance with International Committee of Medical Journal Editors requirements for publication7 and thus more likely to publish in a timely manner. Second, we only studied trials that were published (and indexed via MEDLINE and linked to ClinicalTrials.gov identifiers). Between 50% and 70% of studies registered in ClinicalTrials.gov are eventually published many years after trial completion34; 30% to 50% are never published.

Differences across trial types were generally modest and indicate that timely dissemination of research needs to be uniformly prioritized to enhance science. Many steps must be successfully taken between trial completion and publication, including data management, statistical analysis, and writing, along with processes out of investigators' control, such as peer review. The substantial variation in publication time, from months to years, suggests that there may be opportunities to improve the speed and efficiency with which investigators publish completed studies.

We cannot rule out that study findings may have been disseminated through means other than publication, including scientific meeting presentations. However, with the exception of public results reporting, these alternative dissemination strategies lead to limited public awareness of the research. Given the time required to publish results from these clinical trials, our findings support current federal initiatives requiring results reporting of clinical studies within 12 months of trial completion8 to ensure the timely dissemination of clinical science.

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