2010 – AHA Levels of Evidence10.

Suggested phrases for writing recommendations†
  • should
  • is recommended
  • is indicated
  • is useful/effective/beneficial
  • is reasonable
  • can be useful/effective/beneficial
  • is probably recommended or indicated
  • may/might be considered
  • may/might be reasonable
  • usefulness/effectiveness is unknown/unclear/uncertain or not well established
  • is not recommended
  • is not indicated
  • should not
  • is not useful/effective/beneficial
  • may be harmful

SIZE OF TREATMENT EFFECT

Right-pointing arrow spanning this column to the far right column

    CLASS I

  • Benefit >>> Risk
  • Procedure/Treatment SHOULD be performed/administered
    CLASS IIa

  • Benefit >> Risk

    Additional studies with focused objectives needed
  • IT IS REASONABLE to perform procedure/administer treatment

    CLASS IIb


  • Benefit ≥ Risk
    Additional studies with broad objectives needed; additional registry data would be helpful

  • Procedure/Treatment
    MAY BE CONSIDERED
    CLASS III

  • Risk ≥ Benefit
  • Procedure/Treatment should NOT be performed/administered SINCE IT IS NOT HELPFUL AND MAY BE HARMFUL


ESTIMATE OF CERTAINTY (PRECISION) OF TREATMENT EFFECT

    LEVEL A

  • Multiple populations evaluated*
  • Data derived from multiple randomized clinical trials or meta-analyses


  • Recommendation that procedure or treatment is useful/effective
  • Sufficient evidence from multiple randomized trials or meta-analyses


  • Recommendation in favor of treatment or procedure being useful/effective
  • Some conflicting evidence from multiple randomized trials or meta-analyses


  • Recommendation’s usefulness/efficacy less well established
  • Greater conflicting evidence from multiple randomized trials or meta-analyses


  • Recommendation that procedure or treatment is not useful/effective and may be harmful
  • Sufficient evidence from multiple randomized trials or meta-analyses
    LEVEL B

  • Limited populations evaluated*
  • Data derived from a single randomized trial or nonrandomized studies


  • Recommendation that procedure or treatment is useful/effective
  • Evidence from single randomized trial or nonrandomized studies


  • Recommendation in favor of treatment or procedure being useful/effective
  • Some conflicting evidence from single randomized trial or nonrandomized studies


  • Recommendation’s usefulness/efficacy less well established
  • Greater conflicting evidence from single randomized trial or nonrandomized studies


  • Recommendation that procedure or treatment is not useful/effective and may be harmful
  • Evidence from single randomized trial or nonrandomized studies
    LEVEL C

  • Very limited populations evaluated*
  • Only consensus opinion of experts, case studies, or standard of care


  • Recommendation that procedure or treatment is useful/effective
  • Only expert opinion, case studies, or standard of care


  • Recommendation in favor of treatment or procedure being useful/effective
  • Only diverging expert opinion, case studies, or standard of care


  • Recommendation’s usefulness/efficacy less well established
  • Only diverging expert opinion, case studies, or standard of care


  • Recommendation that procedure or treatment is not useful/effective and may be harmful
  • Only expert opinion, case studies, or standard of care