Table 2. Criteria for Evidence Level of Each Evidence Literature.

Level	Content
1	Research satisfying all of criteria following three
	1) Good reference standard
	2) Consecutive patients study
	3) Blind interpretation
	Systematic review of level 1
	Randomized controlled trial or cross-sectional cohort study that compares index test to comparators
2	Research satisfying all of criteria following two
	1) Good reference standard
	2) Consecutive patients study or blind interpretation
	Systematic review of level 2
	Observational studies that compares index test to comparators
3	Without consistently applied reference standards
4	Case-control study
	Poor or non-independent reference standard
5	Expert opinion

Adapted from Choi et al. Korean J Radiol 2017;18:208–216 (2)