TABLE 2.

Categories indicating the quality of the evidence on which recommendations are based

Level	Definition
I	Evidence from at least one properly randomized controlled trial
II	Evidence from at least one well-designed clinical trial without randomization, from cohort or case-controlled analytical studies, (preferably from more than one centre), from multiple time series, or dramatic results in uncontrolled experiments
III	Evidence from opinions of respected authorities on the basis of clinical experience, descriptive studies, or reports or expert comittees