Table 1 Definition of classes and levels of evidence used in AHA recommendations
From: Clinical review: Critical care management of spontaneous intracerebral hemorrhage
Class I | Conditions for which there is evidence for and/or general agreement that the procedure or treatment is useful and effective |
Class II | Conditions for which there is conflicting evidence and/or a divergence of opinion about the usefulness/efficacy of a procedure or treatment |
Class IIa | Weight of evidence or opinion is in favor of the procedure or treatment |
Class IIb | Usefulness/efficacy is less well established by evidence or opinion |
Class III | Conditions for which there is evidence and/or general agreement that the procedure or treatment is not useful/effective and in some cases may be harmful |
Level of Evidence A | Data derived from multiple randomized trials |
Level of Evidence B | Data derived from a single randomized trial or non-randomized trials |
Level of Evidence C | Expert Opinion or case studies |