Grading of recommendations (adapted from Agency for Healthcare Policy and Research 1994) 5
| Grade | Evidence levels | Description |
| A | Ia, Ib | Requires at least one randomised controlled trial as part of the body of literature of overall good quality and consistency addressing the specific recommendation |
| B | IIa, IIb, III | Requires availability of well-conducted clinical studies but no randomised clinical trials on the topic of recommendation |
| C | IV | Requires evidence from expert committee reports or opinions and/or clinical experience of respected authorities. Indicates absence of directly applicable studies of good quality |