Recommendation grades and levels of evidence
| RCT, randomised controlled trial. | |
| Grade | Evidence |
| A | At least one high quality meta-analysis, systematic review or RCT with a very low risk of bias and directly applicable to the target population; or a systematic review of RCTs 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, bias, or chance 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 meta-analysis, systematic review, or RCT with a very low risk of bias, or a body of evidence consisting principally of well conducted meta-analyses, systematic reviews of RCTs, or RCTs with a low risk of bias, and demonstrating overall consistency of results |
| C | A body of evidence including well conducted case–control or cohort studies with a low risk of confounding, bias, or chance 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 systematic reviews of case–control or cohort studies, or high quality case–control or cohort studies with a very low risk of confounding, bias, or chance and a high probability that the relationship is causal |
| D | Recommendations agreed by Delphi consensus process (based on case–control studies with a high risk of confounding, bias, or chance and a significant risk that the relationship is not causal, or on non-analytic studies (for example, case reports, case series, or expert opinion) |
| GPP | Good practice point based on the clinical experience of the guideline development group, and not specific to CFS/ME |
| NC | A recommendation considered by the Delphi panel but did not reach consensus in two rounds |