There are currently several classifications for levels of evidence. The following is a classification cited in the Journal of Neurosurgery (Editorial. JT Rutka).
|I||i) Randomised controlled trial (RCT); ii) meta-analysis of randomised trials with homogeneous results|
|II||i) Prospective comparative study (therapeutic); ii) meta-analysis of Level II studies or level I studies with inconsistent results|
|III||i) Prospective cohort study; ii) case-control study; iii) meta-analysis of Level III studies|
|V||i)_ Case reports; ii) expert opinion; iii) personal observation|
Rutka JT. Editorial. Classes of evidence in neurosurgery. J Neurosurg., 2017; 126: 1747-1748