Table 1.

Diagnostic test accuracy terminology

Term	Explanation
Index test	Test under evaluation in a diagnostic accuracy study. The accuracy (eg, sensitivity and specificity) of the index test is estimated by comparing the results of the index test with those of a reference standard applied to the same participants. Multiple index tests can be evaluated within the same study
Comparative studies	Studies aiming to compare the diagnostic accuracy of two or more index tests
Reference standard	The method or combination of methods used in the study for establishing the presence or absence of the target condition
Target condition	The disease or condition that the reference standard is expected to detect
Role of the test	The position of the index test relative to other tests in the diagnostic investigation of the same target condition (eg, triage, replacement, add-on, new test)
Intended use of the test	Whether the index test is used for diagnosis, screening, staging, monitoring, surveillance, prognosis, or other purposes
Sensitivity	The proportion of correctly classified participants among those with the target condition
Specificity	The proportion of correctly classified participants among those without the target condition
QUADAS-2	A tool for use in systematic reviews to assess the risk of bias and concerns about applicability of primary diagnostic accuracy studies