Class (strength) of recommendation (COR) | Level of evidence (LOE) |
---|---|
Class I (strong) Benefit >  >  > Risk The procedure should be performed Suggested phrases for recommendations: • Is recommended • Is indicated/useful/effective/beneficial • Should be performed | Level A • High quality evidence from multiple randomized clinical trials or meta-analyses • One or more randomized clinical trials corroborated by high quality registry studies |
Class IIa (moderate) Benefit >  > Risk It is reasonable to perform the procedure. Additional studies with focused objectives needed Suggested phrases for recommendations: • Is resonable • Can be useful/effective/beneficial • Is probably recommended or indicated | Level B • Moderate quality evidence from multiple randomized clinical trials or meta-analyses • Moderate quality evidence from 1 or more well-designed, well-executed nonrandomized studies, observational studied or registry studies or meta-analysis of such studies |
Class IIb (weak) Benefit > Risk The procedure may be considered. Additional studies with broad objectives needed. Additional registry data would be helpful Suggested phrases for recommendations: • May/might be considered • May/might be reasonable • Useful/effectiveness is unknown/unclear/uncertain or not well established | Level C • Randomized or nonrandomized observational or registry studies with limitations of design or execution or meta-analysis of such studies • Physiologic or mechanistic studies in humans • Consensus of expert opinion based on clinical experience |
Class III No Benefit The procedure is not helpful and of no proven benefit Suggested phrases for recommendations: • Is not recommended • Is not indicated • Should not be performed/administered • Is not useful/beneficial/effective | Notes COR and LOE are determined independently (any COR may be paired with any LOE) |
Class III Harm The procedure incurs excess cost without benefit or is harmful to patients Suggested phrases for recommendations: • Is potentially harmful • Causes harm • Associated with excess morbidity/mortality • Should not be performed/administered | A recommendation with LOE B or C does not imply the recommendation is weak. May important clinical questions addressed in guidelines do not lend themselves to clinical trials. Although randomized clinical trials are unavailable, there may be very clear clinical consensus that a particular test is useful or effective |