Which test evaluates the extrinsic pathway of coagulation?

The test that evaluates the extrinsic pathway of coagulation is Prothrombin time (PT). PT specifically assesses the integrity of the extrinsic pathway, which is activated by tissue factor released during injury to blood vessels. This pathway involves the factors such as factor VII, and is essential for the initiation of coagulation.

In a clinical setting, PT is frequently used to monitor patients on anticoagulation therapy, such as those taking warfarin, as it reflects the time taken for blood to clot in relation to the extrinsic pathway. The results of PT can help identify coagulation deficiencies or monitor the effectiveness of anticoagulant therapy.

Other tests listed assess different aspects of coagulation or different pathways. The Apt test is primarily used to check for fetal blood in maternal samples and does not evaluate the extrinsic pathway. Thrombin time measures the time taken for thrombin to convert fibrinogen to fibrin, assessing the common pathway of coagulation, whereas the D-Dimer test is used to rule out thrombotic disorders such as deep vein thrombosis or pulmonary embolism and does not directly evaluate any of the coagulation pathways.