Table 1.
Grades of Recommendation. 52
| Grade of Recommendation | Level of Evidence | Type of Study |
|---|---|---|
| A | 1a | Systematic review of (homogeneous) randomized controlled trials |
| A | 1b | Individual randomized controlled trials (with narrow confidence intervals) |
| B | 2a | Systematic review of (homogeneous) cohort studiesof “exposed” and “unexposed” subjects |
| B | 2b | Individual cohort study/low-quality randomized control studies |
| B | 3a | Systematic review of (homogeneous) case-control studies |
| B | 3b | Individual case-control studies |
| C | 4 | Case series, low-quality cohort or case-control studies |
| D | 5 | Expert opinions based on non-systematic reviews of results or mechanistic studies |