Class I—Conditions for which there is evidence and/or general agreement that a given procedure or treatment is useful and effective.

Class II—Conditions for which there is conflicting evidence and/or a divergence of opinion about the usefulness/efficacy of a procedure or treatment.

Class IIa—Weight of evidence/opinion in favor of usefulness/efficacy.

Class IIb—Usefulness/efficacy is less well established by evidence/opinion

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