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Levels of evidence (32)
| Level of evidence | Requirement |
|---|---|
| Ia | Meta‐analysis of randomised controlled trials |
| Ib | At least one randomised controlled trial |
| IIa | At least one well‐designed controlled trial without randomisation |
| IIb | At least one other type of well‐designed, quasi‐experimental study |
| III | Well‐designed non experimental descriptive studies such as comparative studies, correlation studies, case‐control studies |
| IV | Expert opinions and/or clinical experience of respected authorities |
