Table 2.

Grading of the conclusions and recommendations according to the level of evidence and strength of recommendation

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)