Class I	Conditions for which there is evidence and/or general agreement that a given procedure or therapy is useful and effective
Class II	Conditions for which there is conflicting evidence and/or a divergence of opinion about the usefulness or efficacy of performing the procedure or therapy
Class IIa	Weight of evidence or opinion is in favor of usefulness or efficacy
Class Ilb	Usefulness or efficacy is less well established by evidence or opinion
Class III	Conditions for which there is evidence and/or general agreement that a procedure or therapy is not useful or effective and in some cases may be harmful