Classes of Recommendation

Class I

Conditions for which there is conclusive evidence or, if not, there is general agreement that the procedure is safe and useful/effective.

Class II

Conditions for which there is conflicting evidence and/or divergence of opinion about the safety and usefulness/efficacy of the procedure.

Class IIA

Weight or evidence/opinion in favor of the intervention. Most approve.

Class IIB

Less well-established safety and usefulness/efficacy, without predominance.

Class III

Conditions for which there is evidence and/or general agreement that the procedure is not useful/effective, and in some cases may be harmful.

Levels of Evidence

Level A

Data derived from multiple consistent randomized controlled clinical trials, and/or a robust meta-analysis of randomized clinical trials.

Level B

Data derived from a less robust meta-analysis, one single randomized trial or non-randomized trials (observational).

Level C

Data derived from consensual expert opinion.