protrombiiniindeksin

Protrombiiniindeksi, often abbreviated as PI or PT%, is a laboratory test used to assess the extrinsic pathway of the coagulation cascade. It measures the time it takes for a patient's plasma to clot compared to a control plasma, expressed as a percentage. A normal prothrombin time is typically around 10-13 seconds, but the prothrombin index normalizes this value, with 100% representing the clotting time of a healthy control.

The test is performed by adding thromboplastin (a tissue factor) and calcium ions to a sample of the patient's plasma. Thromboplastin activates factor VII, initiating the extrinsic pathway. This pathway then converges with the intrinsic pathway to form the final common pathway of coagulation, leading to the formation of a fibrin clot. The time taken for this clot to form is measured.

A decreased prothrombin index (meaning a prolonged prothrombin time) can indicate a deficiency in one or more of the vitamin K-dependent clotting factors: factors II, VII, IX, and X, or factor I (fibrinogen). These deficiencies can arise from various conditions, including liver disease, vitamin K deficiency (due to poor diet, malabsorption, or anticoagulant therapy), and certain inherited disorders. Conversely, an increased prothrombin index (shorter clotting time) is less common and can sometimes be seen with thrombotic tendencies, though it is not a primary diagnostic indicator for such conditions. The prothrombin index is crucial in monitoring anticoagulant therapy, particularly with warfarin, where it is used to ensure the medication is within the therapeutic range.