The Prothrombin Time (PT) and International Normalized Ratio (INR) are laboratory tests that assess the extrinsic pathway of coagulation. PT measures the time it takes for blood plasma to clot after adding tissue factor and calcium. The INR standardizes PT results, allowing for consistent interpretation across different laboratories. These tests evaluate the function of several clotting factors, predominantly factors I (fibrinogen), II (prothrombin), V, VII, and X. They are crucial for monitoring anticoagulant therapy and detecting potential bleeding or clotting disorders.
PT / INR
Extrinsic coagulation pathway.