Table 1 Designation of Levels of Evidence

Level I

Evidence obtained from a systematic review of all relevant randomised controlled trials

Level II

Evidence obtained from at least one properly designed randomised controlled trial

Level III-1

Evidence obtained from well-designed pseudo-randomised controlled trials (alternate allocation or some other method)

Level III-2

Evidence obtained from comparative studies with concurrent controls and allocation not randomised (cohort studies), case-control studies, or interrupted time series with a control group

Level III-3

Evidence obtained from comparative studies with historical control, two or more single-arm studies, or interrupted time series without a parallel control group

Level IV

Evidence obtained from case series, either post-test or pre-test and post-test