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.