Table 1.

Rating system for hierarchy of evidence

Level	Description
I	Evidence from a systematic review or meta-analysis of all relevant RCTs or evidence-based clinical practice guidelines based on systematic reviews of RCTs
II	Evidence from at least one well-designed RCT
III	Evidence from well-designed controlled trials without randomization
IV	Evidence from well-designed case-control and cohort studies
V	Evidence from systematic reviews of descriptive and qualitative studies
VI	Evidence from a single descriptive or qualitative study
VII	Evidence from the opinion of authorities and/or reports or expert committees

RCTs – Randomized controlled trials. (Source: Melnyk and Fineout-Overholt)[15]