摘要：Established on 1 June 2005, the University Hospital Medical Information Network Clinical Trials Registry (UMIN-CTR) is the largest clinical trial registry in Japan, and joined the World Health Organization (WHO) registry network in October 2008. Our aim was to understand the registration trend and overall characteristics of Japan domestic, academic (non-industry-funded) clinical trials, which constitute the main body of registrations in UMIN-CTR. In addition, we aimed to investigate the accessibility of clinical trials in UMIN-CTR to people worldwide, as well as the accessibility of clinical trials conducted in Japan but registered abroad to Japanese people in the Japanese language. We obtained the data for registrations in UMIN-CTR from the UMIN Center, and extracted Japan domestic, academic clinical trials to analyze their registration trend and overall characteristics. We also investigated how many of the trials registered in UMIN-CTR could be accessed from the International Clinical Trials Registry Platform (ICTRP). Finally, we searched ClinicalTrials.gov for all clinical trials conducted in Japan and investigated how many of them were also registered in Japanese registries. All of the above analyses included clinical trials registered from 2 June 2005 to 1 June 2010. During the period examined, the registration trend showed an obvious peak around September 2005 and rapid growth from April 2009. Of the registered trials, 46.4% adopted a single-arm design, 34.5% used an active control, only 10.9% were disclosed before trial commencement, and 90.0% did not publish any results. Overall, 3,063 of 3,064 clinical trials registered in UMIN-CTR could be accessed from ICTRP. Only 8.7% of all clinical trials conducted in Japan and registered in ClinicalTrials.gov were also registered in Japanese registries. The International Committee of Medical Journal Editors (ICMJE) announcements about clinical trial registration and the Ethical Guidelines for Clinical Research published by the Japanese government are considered to have promoted clinical trial registration in UMIN-CTR. However, problems associated with trial design, retrospective registration, and publication of trial results need to be addressed in future. Almost all clinical trials registered in UMIN-CTR are accessible to people worldwide through ICTRP. However, many trials conducted in Japan but registered abroad cannot be accessed from Japanese registries in Japanese.
