Researchers and healthcare professionals need to assess the confidence of review results before accepting results of a single systematic review, considering its reputation and influence based on the hierarchy of evidence in an evidence-based practice. A MeaSurement Tool to Assess systematic Reviews 2 (AMSTAR 2), an updated version of AMASTAR, was published in 2017, consists of 16 domains, and is useful as a critical appraisal tool for systematic review of randomized or non-randomized studies of healthcare interventions, or both, in terms of inter-rater agreement and intuitiveness of items. Notably, AMSTAR 2 was not designed to generate an overall score. Moreover, the assessors should evaluate overall confidence in the results of systematic review, by determining critical domains and taking account of the potential impact of critical flaw of each domain on the confidence of the review results.