Recommendations are based on scientific evidence and expert opinion. Each recommended statement includes a Roman numeral (I, II, or III) representing the level of the evidence that supports the recommendation and a letter (A, B, or C) representing the strength of the recommendation.
Class |
|
|---|---|
| I | Evidence and/or general agreement that a given diagnostic evaluation, procedure, or treatment is beneficial, useful, and effective. |
| II | Conflicting evidence and/or a divergence of opinion about the usefulness and efficacy of a diagnostic evaluation, procedure, or treatment. |
| IIa | Weight of evidence and/or opinion is in favor of usefulness and efficacy. |
| IIb | Usefulness and efficacy are less well established by evidence and/or opinion. |
| III | Conditions for which there is evidence and/or general agreement that a diagnostic evaluation, procedure, or treatment is not useful and effective or if it in some cases may be harmful. |
Level |
|
|---|---|
| A | Data derived from multiple randomized clinical trials, meta-analyses, or equivalent. |
| B | Data derived from a single randomized trial, nonrandomized studies, or equivalent. |
| C | Consensus opinion of experts, case studies, or standard of care. |
Adapted from the American College of Cardiology and the American Heart Association Practice Guidelines (AHA, 2011); (Shiffman, 2003).
In some situations, such as for interferon-sparing HCV treatments, randomized clinical trials with an existing standard-of-care arm cannot ethically or practicably be conducted. The US Food and Drug Administration (FDA) has suggested alternative study designs, including historical controls or immediate versus deferred placebo-controlled trials. For additional examples and definitions see FDA link: http://www.fda.gov/downloads/Drugs/GuidanceComplianceRegulatory Information/Guidances/ UCM225333.pdf. In those instances for which there was a single predetermined, FDA-approved equivalency established, panel members considered the evidence as equivalent to a randomized controlled trial for levels A or B.