International Comparison of Data from International Clinical Trials Registry Platform-Registered Clinical Trials

Abstract

Objectives: Our aim was to clarify the study characteristics of countries that have registered clinical trials studies and to calculate the percentage of clinical trials that were registered in each country’s registry, and try to find and evaluate the factors determining that percentage. Design and Methods: The present study is a cross-sec- tional study using data from clinical trials registered from January 1, 2011, to December 31, 2015. Only countries with more than 2000 registered trials were included for further study. Ten countries met that criterion: United States, Japan, Iran, Australia, New Zealand, China, India, Germany, United Kingdom, and Netherland. The percentage of clinical trials that were registered in each country’s registry was calculated, and the factors determining that percentage were sought and analyzed through an exploratory approach. Results: The chi-squared test of independence indicated that the rate of clinical trial registration significantly differed between countries. From the adjusted standardized residuals, the percentage of clinical trials that were registered in the country of origin was higher in the United States, India, Japan, and Australia/New Zealand than in the European Union and China. Conclusion: The United States requires that informed consent documents for clinical trials contain clinical trial registration numbers from ClinicalTrials.gov, which could be the reason for the extremely high percentage of registered clinical trials (94%). Since the European Union does not have this requirement, clinical trials conducted in the European Union do not have to be registered in the countries in which they are conducted.