| Class I |
Conditions for which there is evidence or general
agreement that a given procedure or treatment is useful and
effective. |
| Class II |
Conditions for which there is conflicting evidence
or a divergence of opinion about the usefulness/efficacy of a
procedure or treatment. |
| 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 |
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. |
| Level of Evidence A |
Data derived from multiple randomized clinical
trials. |
| Level of Evidence B |
Data derived from a single randomized trial or
nonrandomized studies. |
| Level of Evidence C |
Consensus opinion of experts. |
