Table 1. Quality appraisal of review articles using the AMSTAR checklist.

AMSTAR: measurement tool for the "assessment of multiple systematic reviews"

Study characteristics	Qu et al. [22]
1. Was an "a priori" design provided (the research question and inclusion criteria should be established before the review)?	Yes
2. Was there duplicate study selection and data extraction?	Yes
3. Was the comprehensive literature search performed?	Yes
4. Was the publication status used as an inclusion criterion?	Yes
5. Was the list of studies (included or excluded) provided?	Yes
6. Are the characteristics of included studies provided?	Yes
7. Was the scientific quality of the included studies assessed and documented?	Yes
8. Was the scientific quality of included studies used appropriately in formulation conclusions?	Yes
9. Were methods used to combine findings of studies appropriate?	Yes
10. Was the likelihood of publication bias assessed?	Yes
11. Was the conflict of interest stated?	Yes