ROC curves of laboratory tests used during the first visit to discriminate between patients with osteomyelitis (n = 37) and patients without osteomyelitis (n = 392). The curves plot the relationship between the true positive rate (Sensitivity, y-axis) and the false positive rate (1 - Specificity, x-axis) at different cut-off titers. The higher the cut-off titer that is chosen, the lower the sensitivity and the higher the specificity, and visa versa. The diagonal reference line (area under curve (AUC) = .5), indicates no discrimination. The greater the distance of the curve from the diagonal, the higher the overall discriminative ability of the test.