What does Prothrombin Time measure?

Study liver anatomy and function with our medical students test. Engage with detailed multiple choice questions, each with hints and explanations. Prepare effectively for your test!

Prothrombin Time measures how long it takes for blood to form a clot after adding tissue factor and calcium, reflecting the function of the extrinsic and common coagulation pathways. In the test, tissue factor activates the pathway that begins with factor VII and continues through factors X, V, II (prothrombin), and fibrinogen; the resulting clot formation time is recorded in seconds. A longer clotting time indicates deficiencies or dysfunction of these factors, which can occur with vitamin K deficiency, liver disease, or anticoagulant therapy such as warfarin. This test is specifically about clot formation time, not about plasma volume, platelet function, or fibrinogen concentration itself, which are measured by different tests.