ESC/ERS guidelines: classes of recommendations
| Definition | |
| Class I | Evidence and/or general agreement that a given treatment or procedure is beneficial, useful, effective. |
| Class II | Conflicting evidence and/or a divergence of opinion about the usefulness/efficacy of the given treatment or procedure. |
| Class IIa | Weight of evidence/opinion is in favour of usefulness/efficacy. |
| Class IIb | Usefulness/efficacy is less well established by evidence/opinion. |
| Class III | Evidence or general agreement that the given treatment or procedure is not useful/effective, and in some cases may be harmful. |
Reproduced from 1 with permission from the publisher.