Studies registered in accounted for an increasing proportion of protocol registrations in medical research

J Clin Epidemiol. 2019 Dec;116:106-113. doi: 10.1016/j.jclinepi.2019.09.005. Epub 2019 Sep 12.


Objective: To compare the recent trends and characteristics of studies registered as in the International Clinical Trials Registry Platform (ICTRP).

Study design and setting: We included all studies on the ICTRP from January 1, 2014, to December 31, 2018. We described the characteristics of included studies and examined whether the proportion of studies registered in on ICTRP increased by interventional design or noninterventional design. We further compared the characteristics of studies registered in to those registered in

Results: We identified 235,830 studies (182,771 studies having interventional design and 53,059 studies having noninterventional design). The proportion of studies registered in among studies registered on ICTRP increased from 2014 to 2018 (38.3% to 53.3% overall, 39.3% to 53.0% for interventional design, and 34.1% to 54.2% for noninterventional design). Studies registered in were more often retrospectively registered as interventional design and lacked sufficient information about target sample sizes than studies registered in irrespective of study design.

Conclusion: Studies registered in increasingly accounted for the proportion of protocol registration among the ICTRP irrespective of study designs since 2014. Systematic reviewers should search ICTRP in addition to

Keywords: Clinical trials registry;; International Clinical Trials Registry Platform; Meta-Research; Protocol registration.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biomedical Research / statistics & numerical data
  • Databases, Factual
  • Humans
  • Registries
  • Research Design / statistics & numerical data
  • Research Design / trends*
  • Sample Size