TABLE 1.

Levels of Evidence for Diagnostic Studies⁵²

	Levels of Evidence for Diagnostic Studies
Level 1	Testing of previously developed diagnostic criteria in a series of consecutive patients (with universally applied reference “gold” standard); systematic review of level 1 studies
Level 2	Development of diagnostic criteria on basis of consecutive patients (with universally applied reference “gold” standard); systematic review of levels 1 and 2 studies
Level 3	Study of nonconsecutive patients (no consistently applied reference “gold” standard); systematic review of level 1 to 3 studies
Level 4	Case-control study; poor reference standard
Level 5	Expert opinion