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Levels of evidence from OCEBM
| Level of evidence | Type of study |
|---|---|
| I | Systematic reviews of RCT or individual RCT (with narrow confidence interval) |
| II | Systematic reviews of cohort studies or individual cohort study |
| III | Systematic reviews of cohort studies or case-control studies, individual case-control study |
| IV | Case-series and poor-quality cohort and case-control studies |
| V | Expert opinion |
