Level | Description |
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, or RCTs with a low risk of bias. |
1- |
Meta-analyses, systematic reviews, 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 and a high probability of a causal relationship. |
2+ |
Well-conducted case-control or cohort studies with a low risk of confounding/bias and a moderate probability that the relationship is causal. |
2- |
Case-control or cohort studies with a high risk of confounding/bias and a significant risk that the relationship is not causal. |
3 |
📝 Non-analytic studies, e.g. case reports or case series. |
4 |
👩⚕️ Expert opinion. |
Grade | Description |
A |
- At least one meta-analysis, systematic review, or RCT rated as 1++ and directly applicable to the target population;
- OR a body of evidence consisting mainly of studies rated as 1+, directly applicable, with consistent results.
|
B |
- A body of evidence including studies rated as 2++, directly applicable, with consistent results;
- OR extrapolated evidence from studies rated as 1++ or 1+.
|
C |
- A body of evidence including studies rated as 2+, directly applicable, with consistent results;
- OR extrapolated evidence from studies rated as 2++.
|
D |
- Evidence level 3 or 4 (non-analytic studies or expert opinion);
- OR extrapolated evidence from studies rated as 2+.
|