Table 1.
Strength of evidence
| Level or GRADE | Criteria |
|---|---|
| Evidence | |
| 1+ | Systematic review or meta-analysis of randomised controlled trials |
| 1 | Randomised controlled trial with adequate power |
| 2+ | Randomised controlled trial that does not meet level 1 criteria |
| 3 | Nonrandomised clinical trial or cohort study |
| 4 | Systematic review including observational studies, before-after studies, cross-sectional studies, cohort studies with non-contemporaneous controls, case-control study |
| 5 | Case series with controls |
| 6 | Case series without controls |
| Recommendation | |
| A | Supported by level 1 or 1+ evidence plus consensus |
| B | Supported by level 2 evidence plus consensus |
| C | Supported by level 3 evidence plus consensus |
| D | Any lower level of evidence plus consensus |
| Grade | |
| High | Further research is unlikely to change our confidence in the estimate of effect |
| Moderate | Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate |
| Low | Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate |
| Very low | Any estimate of effect is very uncertain |