What does the Activated Partial Thromboplastin Time (APTT) measure?

The Activated Partial Thromboplastin Time (APTT) measures the length of time it takes for blood to form a fibrin clot, which is crucial in evaluating the intrinsic pathway of coagulation and the common pathway of the clotting cascade. This test is used primarily to assess the functionality of various clotting factors, particularly when monitoring patients on anticoagulation therapy, such as heparin.

In this context, the APTT provides important information about potential bleeding disorders and can help in diagnosing conditions like hemophilia or disseminated intravascular coagulation (DIC). Monitoring APTT is vital to ensure that anticoagulation levels remain therapeutic and to mitigate the risk of bleeding complications.