Protrombiiniindeksi

Protrombiiniindeksi, often abbreviated as PI or PT ratio, is a measure of how long it takes blood to clot compared to a standard reference sample. It is derived from the prothrombin time (PT) test, which measures the time it takes for blood plasma to clot after the addition of thromboplastin and calcium. The prothrombin time test evaluates the extrinsic and common pathways of the coagulation cascade.

The protrombiiniindeksi is calculated by dividing the prothrombin time of the patient's sample by the prothrombin time of a normal reference plasma sample and multiplying by 100%. A normal protrombiiniindeksi is typically between 80% and 120%. A value below 80% indicates that the patient's blood clotting time is longer than normal, suggesting a potential deficiency in clotting factors or the presence of anticoagulants. Conversely, a value above 120% might indicate a hypercoagulable state, although this is less commonly observed with this specific index.

The protrombiiniindeksi is particularly useful in monitoring warfarin (coumadin) therapy. Warfarin is an anticoagulant that works by inhibiting vitamin K-dependent clotting factors, which are part of the extrinsic pathway assessed by the PT test. Therefore, the protrombiiniindeksi helps physicians adjust warfarin dosage to maintain therapeutic anticoagulation while minimizing the risk of bleeding or clotting. Deviations from the target protrombiiniindeksi range can indicate that the warfarin dose needs to be modified. Other conditions that can affect the protrombiiniindeksi include liver disease, vitamin K deficiency, and disseminated intravascular coagulation.