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  3. Association between trial registration and positive study findings: cross sectional study (Epidemiological Study of Randomized Trials—ESORT)
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Research

Association between trial registration and positive study findings: cross sectional study (Epidemiological Study of Randomized Trials—ESORT)

BMJ 2017; 356 doi: https://doi.org/10.1136/bmj.j917 (Published 14 March 2017) Cite this as: BMJ 2017;356:j917
  1. Ayodele Odutayo, DPhil student1 2,
  2. Connor A Emdin, medical student3,
  3. Allan J Hsiao, PhD student4,
  4. Mubeen Shakir, medical student3,
  5. Bethan Copsey, DPhil student1,
  6. Susan Dutton, senior statistician1,
  7. Virginia Chiocchia, statistician1,
  8. Michael Schlussel, statistician1,
  9. Peter Dutton, statistician1,
  10. Corran Roberts, statistician1,
  11. Douglas G Altman, professor1,
  12. Sally Hopewell, senior research fellow1
  1. 1Centre for Statistics in Medicine, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford OX3 7LD, UK
  2. 2Applied Health Research Centre (AHRC), Li Ka Shing Knowledge Institute of St Michael’s Hospital, Toronto, ON, Canada
  3. 3Faculty of Medicine, Harvard University, Boston, MA, USA
  4. 4Department of Economics, Massachusetts Institute of Technology, Cambridge, MA, USA
  1. Correspondence to: A Odutayo ayodele.odutayo{at}bnc.ox.ac.uk
  • Accepted 31 January 2017

Abstract

Objective To assess whether randomised controlled trials (RCTs) that were registered were less likely to report positive study findings compared with RCTs that were not registered and whether the association varied by funding source.

Design Cross sectional study.

Study sample All primary RCTs published in December 2012 and indexed in PubMed by November 2013. Trial registration was determined based on the report of a trial registration number in published RCTs or the identification of the trial in a search of trial registries. Trials were separated into prospectively and retrospectively registered studies.

Main outcome measure Association between trial registration and positive study findings.

Results 1122 eligible RCTs were identified, of which 593 (52.9%) were registered and 529 (47.1%) were not registered. Overall, registration was marginally associated with positive study findings (adjusted risk ratio 0.87, 95% confidence interval 0.78 to 0.98), even with stratification as prospectively and retrospectively registered trials (0.87, 0.74 to 1.03 and 0.88, 0.78 to 1.00, respectively). The interaction term between overall registration and funding source was marginally statistically significant and relative risk estimates were imprecise (0.75, 0.63 to 0.89 for non-industry funded and 1.03, 0.79 to 1.36 for industry funded, P interaction=0.046). Furthermore, a statistically significant interaction was not maintained in sensitivity analyses. Within each stratum of funding source, relative risk estimates were also imprecise for the association between positive study findings and prospective and retrospective registration.

Conclusion Among published RCTs, there was little evidence of a difference in positive study findings between registered and non-registered clinical trials, even with stratification by timing of registration. Relative risk estimates were imprecise in subgroups of non-industry and industry funded trials.

Footnotes

  • Contributors: CAE and AO conceived and designed the study. AO performed the study analysis. All authors acquired data, analysed and interpreted data, drafted the manuscript, and performed a critical review of the manuscript for intellectual content. AO had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. AO is the guarantor.

  • Funding: This study was not funded. AO, CAE, AJH and MS were supported by the Rhodes Trust. AO was additionally supported by the Clarendon Fund.

  • Competing interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf and declare: no support from any organisation for the submitted work; 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.

  • Ethical approval: Not required.

  • Data sharing: Data and code are available from the corresponding author on request.

  • Transparency: The lead author (AO) affirms that the manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies from the study as planned (and, if relevant, registered) have been explained.

This is an Open Access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.

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