Core outcome set (COS) is an agreed and minimal set of outcomes that should be measured and reported in all clinical trials in specific areas of health or healthcare, which can reduce the heterogeneity of outcomes in similar clinical trials, so that much more trials can merge in systematic reviews. Meanwhile, using COS may be easy to identify potential selective reporting bias in clinical trials. The research of COS has been developed for more than 30 years in western countries. At present there are much more researchers focusing on this area in China. However the status and progress of COS remain unclear. This paper reviewed the quantity of COS, the disease distributions of COS, the geographical locations involved in the development of COS, as well as the methodological progress of COS, so as to clarify the general situation of COS.
The Core Outcome Measures in Effectiveness Trials (COMET) Working Group has published a series of research and reporting guidelines related to core outcome sets since it was established. This article introduces and interprets the Core Outcome Set-STAndardised Protocol Items: the COS-STAP Statement which is developed by the COMET and published in February 2019. It will then be compared with Core Outcome Set-STAndards for Reporting (COS-STAR) and Core Outcome Set-STAndards for Development (COS-STAD), which have been introduced to China. The significance of these guidelines for the development of core outcomes in the field of traditional Chinese medicine is discussed, so as tp draw researchers' attention to this area.