Table 1

Evidence hierarchy

Category of evidenceType of study
IaMeta-analyses of RCT or RCT ≥1 result
IIaControlled study without randomisation
IIbQuasi-experimental study
IIINon-experimental descriptive studies such as comparative, correlation and case–control studies
IVExpert committee reports or opinion or clinical experience of respective authorities, or both
  • Modified from Shekelle et al.5

    RCT, randomised controlled trial.