The Hierarchy of Evidence

The Hierarchy of evidence is based on summaries from the National Health and Medical Research Council (2009), the Oxford Centre for Evidence-based Medicine Levels of Evidence (2011) and Melynyk and Fineout-Overholt (2011). Ι Evidence obtained from a systematic review of all relevant randomised control trials. ΙΙ Evidence obtained from at least one well designed randomised control trial. ΙΙΙ Evidence obtained from well-designed controlled trials without randomisation. IV Evidence obtained from well designed cohort studies, case control studies, interrupted time series with a control group, historically controlled studies, interrupted time series without a control group or with caseseries V Evidence obtained from systematic reviews of descriptive and qualitative studies VI Evidence obtained from single descriptive and qualitative studies VII Expert opinion from clinicians, authorities and/or reports of expert committees or based on physiology