Table 1 Determination of level of evidence: the data from studies was graded according to internationally accepted criteria
1AFrom meta-analysis of randomised controlled trials
1BFrom at least one randomised controlled trial
2AFrom at least one controlled study without randomisation
2BFrom at least one type of quasi-experimental study
3From descriptive studies, such as comparative studies, correlation studies, or case–control studies
4From expert committee reports or opinions and/or clinical experience of respected authorities
  • Trial methodology and other uncontrolled results from any of the studies (including randomised controlled trials) were awarded a lower level of evidence.