Table 3 Evidence hierarchy
1.aEvidence from meta-analysis of randomised controlled trials
1.bEvidence from at least one randomised controlled trial
2.aEvidence from at least one controlled study (without randomisation)
2.bEvidence from at least one type of quasiexperimental study
3Evidence from descriptive studies such as comparative studies, correlation studies or case–control studies
4Evidence from expert committee reports or opinions and/or clinical experience of respected authorities