Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2013 Oct 29;347:f6104.
doi: 10.1136/bmj.f6104.

Non-publication of Large Randomized Clinical Trials: Cross Sectional Analysis

Free PMC article

Non-publication of Large Randomized Clinical Trials: Cross Sectional Analysis

Christopher W Jones et al. BMJ. .
Free PMC article


Objective: To estimate the frequency with which results of large randomized clinical trials registered with are not available to the public.

Design: Cross sectional analysis

Setting: Trials with at least 500 participants that were prospectively registered with and completed prior to January 2009.

Data sources: 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 Registry entries for unpublished trials were reviewed to determine whether results for these studies were available in the results database.

Main outcome measures: The frequency of non-publication of trial results and, among unpublished studies, the frequency with which results are unavailable in the database.

Results: Of 585 registered trials, 171 (29%) remained unpublished. These 171 unpublished trials had an estimated total enrollment of 299,763 study participants. The median time between study completion and the final literature search was 60 months for unpublished trials.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 Of the 171 unpublished trials, 133 (78%) had no results available in

Conclusions: Among this group of large clinical trials, non-publication of results was common and the availability of results in the 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.

Conflict of interest statement

Competing interests: All authors have completed the ICMJE uniform disclosure form at and declare: no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.


Fig 1 Flowchart of included trials
Fig 2 Kaplan-Meier estimate of cumulative publication percentage by time elapsed from trial completion to publication

Comment in

Similar articles

See all similar articles

Cited by 90 articles

See all "Cited by" articles


    1. Emanuel EJ, Wendler D, Grady C. What makes clinical research ethical? JAMA 2000;283:2701-11. - PubMed
    1. Moreno J, Caplan AL, Wolpe PR. Updating protections for human subjects involved in research. Project on Informed Consent, Human Research Ethics Group. JAMA 1998;280:1951-8. - PubMed
    1. Food and Drug Administration Modernization Act of 1997. US Public Law 105-15. (1997, Nov 21); 21 USC 301.
    1. De Angelis C, Drazen JM, Frizelle FA, Haug C, Hoey J, Horton R, et al. Clinical trial registration: a statement from the International Committee of Medical Journal Editors. N Engl J Med 2004;351:1250-1. - PubMed
    1. Moher D, Hopewell S, Schulz KF, Montori V, Gotzsche PC, Devereaux PJ, et al. CONSORT 2010 explanation and elaboration: updated guidelines for reporting parallel group randomised trials. BMJ 2010;340:c869. - PMC - PubMed

Publication types

MeSH terms