A-I: conditions for which there is evidence and/or general agreement that a given treatment is useful and effective, data derived from multiple randomized clinical trials.
A-II:conditions for which there is conflicting evidence and/or divergence of opinion about the usefulness/efficacy of the treatment: data derived from multiple randomized studies.
A-III:conditions for which there is evidence and//or general agreement that the treatment is not useful/effective and in some cases may be harmful: data derived from multiple randomized controlled clinical trials.
B-I: conditions for which there is evidence and/or general agreement that a given treatment is useful and effective: data derived from a single randomized trial or nonrandomized studies.
B-II conditions for which there is conflicting evidence and/or divergence of opinion about the usefulness/efficacy of a procedure/treatment, data derived from a single randomized trial or nonrandomized studies.
B-III: conditions for which there is evidence and/or general agreement that the treatment is not useful/effective and in some cases may be harmful: data derived from a single randomized trial or non-randomized studies.
C-I: conditions for which there is evidence and/or general agreement that a given procedure or treatment is useful and effective: consensus opinion of experts.
C-II:conditions for which there is conflicting evidence and/or divergence of opinion about usefulness/efficacy of the procedure or treatment: consensus opinion of experts.
C-III:conditions for which there is evidence and/or general agreement that the procedure/treatment is not useful/effective and in some cases may be harmful: consensus opinion of experts.