Assessment of the quality of evidence using GRADE
For each systematic review, the quality of the evidence was
assessed using the GRADE method (an acronym for Grading of
Recommendations: Assessment, Development and Evaluation
(http://www.gradeworkinggroup.org/)). GRADE provides guidance
for rating quality of evidence and grading strength of
recommendations in health care and is widely used by international
organisations including WHO [38,39]. GRADE assesses the
quality of a body of evidence based on 5 criteria: risk of bias,
imprecision, inconsistency, indirectness of evidence and publication
bias [40]. Within this review each domain was assessed based
on the following scale: ‘‘no’’ (no risk of bias or imprecision or
inconsistency or publication bias, depending on the domain) (score
0), ‘‘serious’’ (serious risk of bias etc.) (score 21) or ‘‘very serious’’
(very serious risk of bias or publication bias etc.) (score 22). The
basis of assessment was