Table 1.

Definition of levels of evidence for treatment results*

Level I	Level II	Level III	Level IV	Level V
high-quality RCT	Prospective cohort	CC	Case series	Expert opinion
SR of high-quality RCTs	Poor-quality RCT	Retrospective cohort		Case reports1
	SR of above study types	SR of above study types

*Source: Wright JG, Swiontkowski MF, Heckman JD. Introducing levels of evidence to the journal. J Bone Joint Surg Am. Jan 2003;85-A(1):1-3.

Abbreviations: RCT randomized controlled trial, SR systematic review, CC case control study.

¹For this project, case reports were classified as the same level as expert opinion.