What does PTT measure in coagulation testing?

Partial thromboplastin time (PTT) is a laboratory test that measures the time it takes for blood to clot. It assesses the intrinsic and common pathways of coagulation, specifically evaluating factors involved in blood clotting such as factor VIII, IX, XI, and XII, as well as factors I (fibrinogen), II (prothrombin), V, and X.

The test is crucial in diagnosing bleeding disorders, monitoring patients on anticoagulation therapy (like heparin), and evaluating the function of various clotting factors. A prolonged PTT can indicate a deficiency in one or more of these clotting factors, or it may suggest the presence of inhibitors affecting the coagulation cascade.

In contrast, prothrombin time (PT) measures the extrinsic pathway of coagulation and is primarily used to assess anticoagulation therapy with warfarin. Platelet turnover time is not a standard term used in coagulation testing, and pulsatile thrombosis time is not recognized as a relevant measurement in this context. Therefore, the focus on how PTT specifically assesses the intrinsic and common pathways highlights its relevance and importance in coagulation testing.