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Grades of recommendation—adapted from Oxford Center for Evidence-Based Medicine (OCEBM) 2011 [22, 23]
| Level | Evidence (treatment benefits) |
|---|---|
| A | Consistent level 1 studies |
| B | Consistent level 2 or 3 studies or extrapolations from level 1 studies |
| C | Level 4 studies or extrapolations from level 2 or 3 studies |
| D | Level 5 evidence or troublingly inconsistent or inconclusive studies of any level |
