Receiver Operating Characteristic. The ROC is a plot of true positive (sensitivity) against the false positive rate (100-specificity).   The area under this curve (AUC) measures how well a parameter can distinguish between disease and normal. An AUC of 0.5 represents essentially a 50/50 chance that a screening test can predict disease. 0.6 represents a 60% chance and is still a weak predictor. 0.7 is better with AUCs of 0.8 and 0.9 representing tests with good discriminatory ability.