Box 3.
Revised grading system for recommendations in evidence based guidelines
- Levels 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 or RCTs, or RCTs with a high risk of bias
- 2++ 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
- 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, eg case reports, case series
- 4 Expert opinion
- Grades of recommendations
- A At least one meta-analysis, systematic review, or RCT rated as 1++ 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+