Appendix 2 Recommendation grades and levels of evidence in Scottish guidelines
| Grades of recommendation | |
|---|---|
| RCT, randomised controlled trial. | |
| A | At least one high quality meta analysis, systematic review of RCTs, or RCT with a very low risk of bias, and directly applicable to the target population; or |
| A body of evidence consisting principally of well conducted meta-analyses, systematic reviews of RCTs, or RCTs with a low risk of bias, directly applicable to the target population, and demonstrating overall consistency of results. | |
| B | A body of evidence including high quality systematic reviews of case–control or cohort studies, or high quality case–control or cohort studies with a very low risk of confounding or bias and a high probability that the relationship is causal, directly applicable to the target population and demonstrating overall consistency of results; or |
| Extrapolated evidence from high quality or well conducted meta analyses, systematic reviews of RCTs, or RCTs with a low or very low risk of bias | |
| C | A body of evidence including well conducted case–control or cohort studies with a low risk of confounding or bias and a moderate probability that the relationship is causal, directly applicable to the target population and demonstrating overall consistency of results; or |
| Extrapolated evidence from high quality systematic reviews of case–control or cohort or studies or high quality case–control or cohort studies with a very low risk of confounding or bias and a high probability that the relationship is causal. | |
| D | Non-analytic studies—for example, case reports, case series, or expert opinion; or |
| Extrapolated evidence from well conducted case–control or cohort studies with a low risk of confounding or bias and a moderate probability that the relationship is causal. | |