Grades of recommendation(ranging from A1 to C4)
| Grades of recommendation | |
| A | Consistent evidence = clear outcome |
| B | Inconsistent evidence = unclear outcome |
| C | Insufficient evidence = consensus |
| Suffix for recommendations | |
| Preventative and therapeutic intervention studies# | |
| 1 | SR or MA of RCTs |
| 2 | 1 RCT or >1 RCT, but no SR or MA |
| 3 | 1 cohort study or >1 cohort study, but no SR or MA |
| 4 | Other |
| Diagnostic, prognostic, aetiological and other types of studies | |
| 1 | SR or MA of cohort studies |
| 2 | 1 cohort study or >1 cohort study, but no SR or MA |
| 3 | Other |
SR: systematic review; MA: meta-analysis; RCT: randomised controlled trial. #: including harm.