The ROC plots sensitivity against 1 - specificity (ie, the false-positive rate). Cutoff values for the diagnostic test vary along the length of the dashed curve, reflecting the interchange between sensitivity and specificity. The area under the ROC curve represents the accuracy of the test. A test that performs no better than chance would be represented by a straight line (solid line) with an area under the ROC of 0.5. A near-perfect test would have a rectangular configuration (dotted line) with an area under the ROC approaching 1.00.
