TABLE 2.
Applying American College of Cardiology/American Heart Association Class of Recommendation and Level of Evidence to Clinical Strategies, Interventions, Treatments, or Diagnostic Testing in Patient Care* (Updated May 2019)
| CLASS (STRENGTH) OF RECOMMENDATION | |
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| CLASS 1 (STRONG) | Benefit >>> Risk |
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| |
| Suggested phrases for writing recommendations: | |
| • Is recommended | |
| • Is indicated/useful/effective/beneficial | |
| • Should be performed/administered/other | |
| • Comparative-Effectiveness Phrases†: | |
| – Treatment/strategy A is recommended/indicated in preference to treatment B | |
| – Treatment A should be chosen over treatment B | |
|
| |
| CLASS 2a (MODERATE) | Benefit >> Risk |
|
| |
| Suggested phrases for writing recommendations: | |
| • Is reasonable | |
| • Can be useful/effective/beneficial | |
| • Comparative-Effectiveness Phrases†: | |
| – Treatment/strategy A is probably recommended/indicated in preference to treatment B | |
| – It is reasonable to choose treatment A over treatment B | |
|
| |
| CLASS 2b (WEAK) | Benefit ≥ Risk |
|
| |
| Suggested phrases for writing recommendations: | |
| • May/might be reasonable | |
| • May/might be considered | |
| • Usefulness/effectiveness is unknown/unclear/uncertain or not well-established | |
|
| |
| CLASS 3: No Benefit (MODERATE) (Generally, LOE A or B use only) | Benefit = Risk |
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| Suggested phrases for writing recommendations: | |
| • Is not recommended | |
| • Is not indicated/useful/effective/beneficial | |
| • Should not be performed/administered/other | |
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| Class 3: Harm (STRONG) | Risk > Benefit |
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| Suggested phrases for writing recommendations: | |
| • Potentially harmful | |
| • Causes harm | |
| • Associated with excess morbidity/mortality | |
| • Should not be performed/administered/other | |
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| |
| LEVEL (QUALITY) OF EVIDENCE ‡ | |
|
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| LEVEL A | |
|
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| • High-quality evidence‡ from more than 1 RCT | |
| • Meta-analyses of high-quality RCTs | |
| • One or more RCTs corroborated by high-quality registry studies | |
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| LEVEL B-R | (Randomized) |
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| • Moderate-quality evidence‡ from 1 or more RCTs | |
| • Meta-analyses of moderate-quality RCTs | |
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| LEVEL B-NR | (Nonrandomized) |
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| • Moderate-quality evidence‡ from 1 or more well-designed, well-executed nonrandomized studies, observational studies, or registry studies | |
| • Meta-analyses of such studies | |
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| LEVEL C-LD | (Limited Data) |
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| • 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 | |
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| LEVEL C-EO | (Expert Opinion) |
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| • Consensus of expert opinion based on clinical experience | |
COR and LOE are determined independently (any COR may be paired with any LOE).
A recommendation with LOE C does not imply that the recommendation is weak. Many important clinical questions addressed in guidelines do not lend themselves to clinical trials. Although RCTs are unavailable, there may be a very clear clinical consensus that a particular test or therapy is useful or effective.
The outcome or result of the intervention should be specified (an improved clinical outcome or increased diagnostic accuracy or incremental prognostic information).
For comparative-effectiveness recommendations (COR 1 and 2a; LOE A and B only), studies that support the use of comparator verbs should involve direct comparisons of the treatments or strategies being evaluated.
The method of assessing quality is evolving, including the application of standardized, widely-used, and preferably validated evidence grading tools; and for systematic reviews, the incorporation of an Evidence Review Committee.
COR indicates Class of Recommendation; EO, expert opinion; LD, limited data; LOE, Level of Evidence; NR, nonrandomized; R, randomized; and RCT, randomized controlled trial.