Level | Study design |
---|---|
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 pseudo-randomised 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. |