Class I: conditions for which there is evidence or general agreement that a given procedure or treatment is useful and effective

Class II: conditions for which there is conflicting evidence or a divergence of opinion about the usefulness or efficacy of a procedure or treatment

Class IIa: weight of evidence or opinion favors usefulness or efficacy

Class IIb: usefulness or efficacy is less well established by evidence or opinion

Class III: conditions for which there is evidence or general agreement that a given procedure or treatment is not useful or effective, and in some cases may be harmful