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Level of evidence as described by Wright et al10
| Level of evidence | Type of study |
|---|---|
| I | 1. RCT 2. Systematic review of level I RCT |
| II | 1. Prospective cohort study 2. Poor-quality RCT 3. Systematic review level II studies |
| III | 1. Case-control study 2. Retrospective cohort study 3. Systematic review of level III studies |
| IV | Case series (no, or historical, control group) |
| V | Expert opinion |
RCT, randomised control trial
