Figure 5. Illustration of the receiver operating characteristic (ROC) curves for the ability of various coagulation assays to identify patients with greater than 400 ml of cumulative chest tube drainage in the first 4 postoperative hours. Sensitivity and specificity rates were calculated using Bayes' theorem (see text), and the area under the ROC curve was calculated using logistic regression analysis in a series of patients who did not receive either desmopressin acetate or platelet transfusions in the perioperative interval (n = 83). The area under the curve for each of the assays included in this graph are as follows: % Maximal clot ratio values in channel 5 (CRCh5, 0.94), bleeding time (BT, 0.88), prothrombin time (PT, 0.53), activated partial thromboplastin time (APTT, 0.55), and platelet count (PLT, 0.52).