Table 1

ACCF/AHA/SCAI PCI guideline evidence definitions by class and level of recommendations9 10

Class IClass IIaClass IIbClass III
Level A
 ACCSufficient evidence from multiple randomised trials or meta-analysesSome conflicting evidence from multiple randomised trials or meta-analysesGreater conflicting evidence from multiple randomised trials or meta-analysesSufficient evidence from multiple randomised trials or meta-analyses
 ESCEvidence/general agreement of efficacy
Data from multiple randomised trials or meta-analyses
Weight of evidence/opinion in favour of efficacy
Data from multiple randomised trials or meta-analyses
Efficacy less well established by evidence/opinion
Data from multiple randomised trials or meta-analyses
Evidence/agreement of non-efficacy or possible harm Data from multiple randomised trials or meta-analyses
Level B
 ACCEvidence from single randomised trial or non-randomised studiesSome conflicting evidence from a single randomised trial or non-randomised studiesGreater conflicting evidence from a single randomised trial or non-randomised studiesEvidence from a single randomised trial or non-randomised studies
 ESCEvidence/general agreement of efficacy
Data from single randomised trial or large non-randomised studies
Weight of evidence/opinion in favour of efficacy
Data from single randomised trial or large non-randomised studies
Efficacy less well established by evidence/opinion
Data from single randomised trial or large non-randomised studies
Evidence/agreement of non-efficacy or possible harm
Data from single randomised trial or large non-randomised studies
Level C
 ACCOnly expert opinion, case studies or SOCOnly diverging expert opinion, case studies or SOCOnly diverging expert opinion, case studies or SOCOnly expert opinion, case studies or SOC
 ESCEvidence/general agreement of efficacy
Consensus of experts and/or non-randomised studies
Weight of evidence/opinion in favour of efficacy
Consensus of experts and/or non-randomised studies
Efficacy less well established by evidence/opinion
Consensus of experts and/or non-randomised studies
Evidence/agreement of non-efficacy or possible harm
Consensus of experts and/or non-randomised studies
 RecommendationIs recommended/indicatedCan be useful/effective/beneficial or indicatedMay be considered/reasonableNo Benefit/not recommended or potentially harmful
  • ACC (American College of Cardiology), ESC (European Society of Cardiology); PCI (percutaneous coronary intervention); SOC (standard of care).