• Guiping Hu, Yanan Hu, and Siyan Zhan.
• Department of Occupational and Environmental Health, School of Public Health, Peking University, Beijing 100191, China.
• Zhonghua Liu Xing Bing Xue Za Zhi. 2016 Mar 1; 37 (3): 439-42.

AbstractRandomized controlled trial (RCT) can be designed as explanatory trial and pragmatic/practical trial (PCT) for clinical effect evaluation. The pragmatic/practical trial reflects the intervention effect under actual clinical condition, which has relatively good extrapolation, but its internal validity is relatively poor. In contrast, explanatory trials conducted under ideal conditions have better inner validity but inferior external validity. However, in the design of RCT, PCT and explanatory trials are not always opposite. Many RCTs have the properties of the two designs at the same time, Pragmatic-explanatory continuum indicator summary (PRECIS) can be used in the design of RCT for the balance between internal validity and external validity. There are few available reports about the application of PRECIS in China at present, so this paper summarizes the basic principles, characteristics of PRECIS and the application of PRECIS in order to provide reference for the clinical trial design in China.

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