Table 1b.
Oxford Centre for Evidence-Based Medicine grades of recommendation.20
| Grade of evidence | Definition |
|---|---|
| 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 |
*
“Extrapolations” refer to the use of data in a situation that has potentially clinically important differences from the original study situation.