Table 1.

Class of recommendations (COR) and corresponding definition.

COR	Definition
Class I (strong)	Evidence and/or general agreement that a given treatment or procedure is beneficial, useful, and effective. (Benefit ≫ Risk)
Class II	Conflicting evidence and/or a divergence of opinion about the usefulness/efficacy of the given treatment or procedure.
Class IIa (moderate)	Weight of evidence/opinion is in favor of usefulness/efficacy. (Benefit >Risk)
Class IIb (weak)	Usefulness/efficacy is less well established by evidence/opinion. (Benefit ≥Risk)
Class III	Evidence or general agreement that the given treatment or procedure is not useful/effective, and in some cases may be harmful.
Class III: No benefit	Benefit = Risk
Class III: Harm	Benefit <Risk