Level of evidence | Definition |
---|---|
I | A systematic review of level II studies |
II | A randomised controlled trial |
III | A pseudorandomised controlled trial (i.e. alternate allocation or some other method) |
III-2 | A comparative study with concurrent controls (i.e. non-randomised experimental trial, cohort study, case–control study) |
III-3 | A comparative study without concurrent controls (i.e. historical cohort study, two or more single arm study) |
IV | Case series |
EO | Expert opinion – where evidence was absent or unreliable and advice was formulated based on the clinical judgement and experience of experts in the field |