Table 1: Grading system for recommendations.

Classification description

Class of evidence
Class 1Conditions for which there is evidence and/or general agreement that a given diagnostic evaluation procedure or treatment is beneficial, useful, and effective
Class 2Conditions for which there is conflicting evidence and/or a divergence of opinion about the usefulness/efficacy of a diagnostic evaluation, procedure, or treatment
Class 2aWeight of evidence/opinion is in favour of usefulness/efficacy
Class 2bUsefulness/efficacy is less well established by evidence/opinion
Class 3Conditions for which there is evidence and/or general agreement that a diagnostic evaluation and procedure/treatment is not useful/effective and in some cases may be harmful

Grade of evidence
Level AData derived from multiple randomized clinical trials or meta-analyses
Level BData derived from a single randomized trial or nonrandomized studies
Level COnly consensus opinions of experts, case studies, or standard-of-care

Adapted from [7].