Table 1.

Signaling questions in the QUADAS-2

Domain	Patient selection	Index test	Reference standard	Flow and timing
Signaling questions (yes/no/unclear)	1 Was a consecutive or random sample of patients enrolled?	4 Were the index test results inter preted without knowledge of the results of the reference standard?	5 Is the reference standard likely to correctly classify the target condition?	7 Was there an appropriate interval between index test(s) and reference standard?
	2 Was a case-control design avoided?		6 Were the reference standard results interpreted without know ledge of the results of the index test?	8 Did all patients receive a reference standard?
	3 Did the study avoid inappropriate exclusions?			9 Were all patients included in the analysis?

Abbreviation: QUADAS-2, The Quality Assessment Diagnostic Accuracy Studies statement-2.