Selection of primary studies and data extraction
After retrieving the references, the
titles and abstracts were screened in duplicate by two
reviewers. Once it is determined that
relevant studies may be included, the full text will be screened. If
there was any doubt about eligibility, a third reviewer will be the
arbitrator. Upon completion of the above work, two reviewers used a
tested data extraction form to abstract data independently. This
included the characteristics of the references, the year of publication,
first author, study period, definition of PUL and the outcomes,
experimental design, study methodology, management protocol, and final
clinical results.