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Grades of Recommendation (Oxford Centre for Evidence-based Medicine—March 2009) [107].
| Grade | Contents |
|---|---|
| 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 |
