Answer: a, c, d Coagulation tests include prothrombin time (PT), which measures the intrinsic and extrinsic pathways of fibrinogen production and is the most common method for measuring a level of oral anticoagulant therapy. The activated partial thromboplastin time (aPTT) identifies the abnormalities of the contact and intrinsic phases of coagulation. Values of aPTT have variably been shown to correlate with heparin dosages and serum heparin levels and are therefore most commonly used in monitoring heparin therapy. It is of no value in long-term management of patients on oral Warfarin therapy. Thrombin clotting time (TCT) is the measure of the time it takes for exogenously administered thrombin to turn plasma fibrinogen into fibrin clot. It is extremely sensitive to levels of heparin and is an excellent measure of measuring the level of heparin-induced anticoagulation. The beauty of the TCT is that it is not specific for any disease condition; thus it may be used to differentiate factor deficiencies from the presence of heparin, or to separate lupus anticoagulant from abnormalities in fibrinogen levels. The whole blood activated clotting time (ACT) is a measurement of the ability of whole blood to clot, and as such, is an available technique for monitoring heparin levels intraoperatively. The ACT responds in a linear fashion to increasing heparin dosage and correlates well with the observed clinical anticoagulation. Adequate anticoagulation for extracorporeal circulation is defined as an ACT of 480 seconds or more while for peripheral vascular applications, values of 250 seconds or greater are considered appropriate