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Levels of evidence—adapted from Oxford Center for Evidence-Based Medicine (OCEBM) 2011 [22]
| Level | Evidence (treatment benefits) |
|---|---|
| I | Systematic review or meta-analysis of RCTs, high-quality individual RCTs |
| II | Systematic review or meta-analysis of cohort studies, low-quality individual RCTs, prospective studies |
| III | Systematic review of case–control studies, retrospective cohort studies |
| IV | Case series |
| V | Expert opinion |
Abbreviation: RCTs randomized controlled trials
