Guidance
Appendix A: Grading scheme
Appendix A: Grading scheme
The recommendation grading scheme and hierarchy of evidence used in this guideline are adapted from the Scottish Intercollegiate Guidelines Network (SIGN 50: A guideline developers' handbook), and summarised in the tables below.
|
Recommendation grade |
Evidence |
|
A |
At least one meta-analysis, systematic review, or randomised controlled trial (RCT) rated as 1++ (see table on page 17), and directly applicable to the target population, or A systematic review of RCTs or a body of evidence consisting principally of studies rated as 1+, directly applicable to the target population, and demonstrating overall consistency of results |
|
B |
A body of evidence including studies rated as 2++, directly applicable to the target population, and demonstrating overall consistency of results, or Extrapolated evidence from studies rated as 1++ or 1+ |
|
C |
A body of evidence including studies rated as 2+, directly applicable to the target population and demonstrating overall consistency of results, or Extrapolated evidence from studies rated as 2++ |
|
D |
Evidence level 3 or 4, or Extrapolated evidence from studies rated as 2+, or Formal consensus |
|
D (GPP) |
A good practice point (GPP) is a recommendation for best practice based on the clinical experience of the Guideline Development Group |
|
Level of evidence |
Type of evidence |
|
1++ |
High-quality meta-analyses, systematic reviews of RCTs, or RCTs with a very low risk of bias |
|
1+ |
Well-conducted meta-analyses, systematic reviews of RCTs, or RCTs with a low risk of bias |
|
1– |
Meta-analyses, systematic reviews of RCTs, or RCTs with a high risk of bias |
|
2++ |
High-quality systematic reviews of case–control or cohort studies 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 |
|
2+ |
Well-conducted case–control or cohort studies with a low risk of confounding, bias or chance, and a moderate probability that the relationship is causal |
|
2– |
Case–control or cohort studies with a high risk of confounding, bias or chance, and a significant risk that the relationship is not causal |
|
3 |
Non-analytic studies (for example, case reports, case series) |
|
4 |
Expert opinion, formal consensus |