In Reply Zhang and Tang asked for more information on the search strategy of our study.1 Details of the methods were provided in our previously published protocol and the search strategy was included in Supplement 2. In the PubMed search, there were no limits, and all terms were searched using text words, so Medical Subject Headings (MeSH) terms were automatically included. Text-word searches with no limits were used in the other English-language databases.2 Consequently, the database searches were comprehensive.