Validity and grading of recommendations
| Category of evidence | Grading of recommendations | |
|---|---|---|
| Meta-analysis of randomised controlled trials | Ia | A |
| Randomised controlled trial | Ib | A |
| Well-designed controlled study without randomisation | IIa | B |
| Well-designed quasi-experimental study | IIb | B |
| Non-experimental descriptive study | III | B |
| Expert opinion | IV | C |