| I |
Evidence obtained from a systematic review of all relevant randomised controlled trials |
| II |
Evidence obtained from at least one properly-designed randomised controlled trial |
| III-1 |
Evidence obtained from well-designed pseudorandomised controlled trials (alternate allocation or some other method) |
| III-2 |
Evidence obtained from comparative studies (including systematic reviews of such studies) with concurrent controls and allocation not randomised, cohort studies, case-control studies, or interrupted time series with a control group |
| 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 |
| IV |
Evidence obtained from case series, either post-test or pre-test/post-test |
