in diagnostic accuracy studies, the outcomes from one or more diagnostic tests under evaluation (the index test/s) are compared with outcomes from a reference standard test. These outcomes are measured in individuals who are suspected of having the condition of interest. The term accuracy refers to the amount of agreement between the index test and the reference standard test in terms of outcome measurement. Diagnostic accuracy can be expressed in many ways, including sensitivity and specificity, likelihood ratios, diagnostic odds ratio, and the area under a receiver operator characteristic (ROC) curve (Bossuyt et al 2003)