Figure 2. Receiver operating characteristic curves for the ability of tests of coagulation function to identify patients with blood loss of more than an average of 200 ml/h and 100 ml/h for each of the first 4 h after operation. PLT = platelet count, PT = prothrombin time, aPTT = activated partial thromboplastin time, Ch5 = platelet activated clotting test channel 5, Ch6 = platelet activated clotting test channel 6. A test that lies on the line of identity has no predictive value.