In a Receiver Operating Characteristic (ROC) curve the true positive rate (Sensitivity) is plotted in function of the false positive rate (1 -Specificity) for different cut-off points. A test with perfect discrimination has a ROC plot that passes through the upper left corner (100% sensitivity, 100% specificity). The nearer the ROC plot is to the upper left corner, the higher the overall accuracy of the test.5 The larger the area under the ROC the better the diagnostic test. If the area is 1.0, this is a perfect test, because it achieves both 100% sensitivity and 100% specificity. If the area is 0.5, then this test is no better than flipping a coin as it has only 50% sensitivity and 50% specificity.
An aggregate score of five (sensitivity 86.6%, specificity 72.2%) was identified as the trigger score to enact a rapid response team call (See Table 3). This would allow for early recognition and intervention in 86.6% of children developing critical illness in acute care.