Prothrombin Time ( PT )

The Prothrombin Time (PT) test is a laboratory assay that evaluates the clotting ability of blood by measuring the time it takes for a fibrin clot to form after the addition of calcium and a tissue factor activator. The PT primarily assesses the integrity of the extrinsic and common coagulation pathways, which involve factors outside the blood vessel (e.g., tissue factor) and factors shared by both the intrinsic and extrinsic pathways (e.g., factors II, V, VII, X), respectively. The PT test is commonly used to screen for and monitor coagulation disorders, including deficiencies or abnormalities in coagulation factors, liver dysfunction, vitamin K deficiency, and the presence of anticoagulant medications or inhibitors. Elevated PT values may indicate conditions such as liver disease, vitamin K deficiency, disseminated intravascular coagulation (DIC), or the presence of anticoagulant drugs (e.g., warfarin). Conversely, shortened PT values may suggest hypercoagulable states or the use of procoagulant medications. The PT test is routinely performed in clinical settings, preoperative evaluations, monitoring anticoagulant therapy (e.g., warfarin dosing), assessing liver function, and diagnosing coagulation disorders.