Literature selection and data extraction
Two researchers independently searched the literature, screened and collected data according to the inclusion and exclusion criteria. In case of disagreement, consult the third researcher. After computerized de-duplication using the literature management software, investigators read the title and abstract alone for initial screening, and then obtained the full text for re-screening, and extracted: basic information such as country, year, and organization of publication, information related to guideline quality evaluation and guideline recommendations for content analysis, etc.