2.4 Quality assessment and data extraction
The study quality was evaluated by two investigators (L-MF and L-MJ)
using the Newcastle–Ottawa Scale (NOS) for observational studies and
Delphi consensus criteria for randomized controlled study (RCTs). The
NOS system consisted of eight questions with nine possible points. A
star system was used to judge the data according to the selected
populations and the comparability of the groups and exposure/outcome of
interest. A study with NOS ≥7 was judged to be a study of good
quality8. The Preferred
Reporting Items for Systematic Reviews and Meta-analyses Amendment to
the Quality of Reporting of Meta-analyses Statement and recommendations
from the Cochrane Collaboration in epidemiology were followed while
performing the present systematic review. Data extraction was conducted
by mutual agreement, and all potential disagreements were solved by
consensus 9,
10.