ACC AHA guidelines classification scheme

Overview
The Class designation is used to indicate whether a therapy is recommended or not and the certainty surrounding that recommendation.

Class I: Benefit >>> Risk
Conditions for which there is evidence and/or general agreement that a given procedure or treatment is beneficial, 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: Benefit >> Risk
Weight of evidence/opinion is in favor of usefulness/efficacy.

Class IIb: Benefit ≥ Risk
Usefulness/efficacy is less well established by evidence/opinion.

Class III: Risk ≥ Benefit
Conditions for which there is evidence and/or general agreement that a procedure/treatment is not useful/effective and in some cases may be harmful.

Class III: No Benefit
Is not recommended, not indicated, should not be performed/ administered/ other. Is not useful/beneficial/effective.

Class III: Harm
Potentially harmful, causes harm, associated with excess morbidity/mortality. Should not be performed/administered/other.

Use the Level of Evidence designation to indicate the strength of the data associated with that recommendation.

Level of Evidence A:
Data derived from multiple randomized clinical trials or meta-analyses.

Level of Evidence B:
Data derived from a single randomized trial, or nonrandomized studies.

Level of Evidence C:
Only consensus opinion of experts,case studies, or standard-of-care.