Table 2.

Comparison of evidence rating systems used in heart failure guidelines

CCS/CHFS	ESC	AHA/ACC/HFSA
GRADE certainty of evidence: Rated as high, moderate, low, or very low.	Comparable classification using “level of evidence”
High: Further research is very unlikely to change our confidence in the estimate of effect. No serious risk of bias, inconsistency, imprecision, indirectness, or publication bias	A: Data derived from multiple randomized clinical trials or meta-analyses	A: High-quality evidence from more than 1 RCT, meta-analyses of high-quality RCTs, or one or more RCTs corroborated by high-quality registry studies
Moderate: Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate.	B: Data derived from a single randomized clinical trial or large nonrandomized studies	B: •R: Moderate-quality evidence from 1 or more RCTs, or meta-analyses of moderate-quality RCTs •NR: Moderate-quality evidence from 1 or more well-designed, well-executed nonrandomized studies, observational studies, or registry studies; meta-analyses of such studies
Low: Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate.	-	C-LD: Randomized or nonrandomized observational or registry studies with limitations of design or execution; meta-analyses of such studies; physiological or mechanistic studies in human subjects
Very low: Any estimate of effect is very uncertain.	C: Consensus of opinion of the experts and/or small studies, retrospective studies, registries	C-EO: Consensus of expert opinion based on clinical experience
GRADE strength of recommendation: CCS uses strong or weak as qualifiers of strength of recommendations based on consideration of quality of evidence, difference between desirable and undesirable effects (ie, tradeoffs), values and preferences, and cost or value considerations.	Comparable classification of strength of recommendation
Strong recommendation in favour of an intervention	Class I: Evidence and/or general agreement that a given treatment or procedure is beneficial, useful, effective	Class 1 (strong): Benefit > > > Risk
Weak recommendation in favour of an intervention	Class II: Conflicting evidence and/or a divergence of opinion about the usefulness/efficacy of the given treatment or procedure •IIa: Weight of evidence/opinion is in favour of usefulness/ efficacy •IIb: Usefulness/efficacy is less well established by evidence/opinion	Class 2a (moderate): Benefit > > Risk Class 2b (weak): Benefit ≥ Risk
Weak recommendation against an intervention	Class III: Evidence or general agreement that the given treatment or procedure is not useful/effective, and in some cases may be harmful	Class 3: No benefit (moderate): Benefit = Risk
Strong recommendation, against an intervention		Class 3: Harm (strong): Risk > Benefit

Adapted from Klugar et al.¹¹ ACC, American College of Cardiology; AHA, American Heart Association; CCS, Canadian Cardiovascular Society; CHFS, Canadian Heart Failure Society; EO, expert opinion; ESC, European Society of Cardiology; GRADE, Grading of Recommendations, Assessment, Development and Evaluations; HFSA, Heart Failure Society of America; LD, limited data; RCT, randomized controlled trial.