Grading of the nature of the evidence for each workshop proposition
| Nature of evidence | Study design | Study execution | Consistency | Directness of evidence |
|---|---|---|---|---|
| *RCTs, randomised controlled trials. | ||||
| Adapted from: Mason J, Eccles M. Guideline Recommendation and Evidence Grading (GREG): a new grading method for Clinical Guideline Development Groups. University of Newcastle upon Tyne: Centre for Health Services Research, 2003; report 109. | ||||
| Exceptions that can alter the quality of grading: sparse data (few events); use of data not in its initial randomisation, or apparent publication bias, can lower the quality; a very strong association can raise the quality. | ||||
| Coding notes: important flaws occur when the highest standards of research that could be achieved by a study are not applied; consistency occurs at two levels—design (consistent methods, patients, outcomes) and statistical (a test of homogeneity of a summary estimate when the level of design consistency is acceptable and meta-analysis appropriate); directness: “direct evidence”: relevant patient benefits and harms are measured in studies; “strong indirect”: the surrogate end point is strongly related to desirable end points, or that direct evidence is available for a sufficiently related patient group; “weak indirect”: the relationship between the study outcomes and patient benefits or harms is insufficient. | ||||
| A | Meta-analysis of RCTs* (for interventions) | No important flaws | Consistent | Direct or strong indirect |
| RCTs (for interventions) | ||||
| Non-randomised studies (for diagnosis and prognosis) | ||||
| B | Meta-analysis of RCTs or RCTs (for interventions) | Important flaw or inconsistent or weak indirect | ||
| Non-randomised studies (for diagnosis or prognosis) | Important flaw or inconsistent or weak indirect | |||
| Non-randomised controlled studies (for interventions) | No important flaws | Consistent | Direct or strong indirect | |
| C | Non-randomised controlled studies (for interventions) | Important flaw or inconsistent or weak indirect | ||
| Meta-analyses or RCTs with a combination of important flaws and inconsistency and/or indirect evidence | ||||
| D | Other evidence (not expert opinion) | |||
| E | Expert opinion | |||