Selection strategy:
After a primary search, all extracted studies found from searches were
uploaded into endnote software (EndNote X6, Thomson Reuters, New York)
for screening. Titles and abstracts of papers were screened using the
search strategy. Articles were evaluated independently by two authors
and selected according to the inclusion criteria. Studies including
eligibility criteria in the screening of title and abstract were elected
to be checked by full-text. On the basis of the qualified data, we used
a standardized form to elect the all categorized studies eligible for
inclusion in this review. Contradictions between the authors were
resolved by third researcher or consensus.