Level | Conclusion based on |
A | Systematic review (A1) or at least 2 independent studies with evidence level A2 (“there is evidence that…”) |
B | One study with evidence level A2 or at least 2 independent studies with evidence level B (“it is likely that…”) |
C | One study with evidence level B or level C (“there are indications that…”) |
D | Expert opinion (“the working group recommends…”) |
Level | Recommendation |
I | Strong recommendation |
II | Weak recommendation (suggestion) |