Activated clotting time
Activated clotting time, also known as activated coagulation time, is a test of coagulation.
The ACT test can be used to monitor anticoagulation effects, such as high-dose heparin before, during, and shortly after procedures that require intense anticoagulant administration, such as cardiac bypass, interventional cardiology, thrombolysis, extra-corporeal membrane oxygenation, and continuous dialysis. It measures the seconds needed for whole blood to clot upon activation of the intrinsic pathway by the addition of factor XII activators. The clotting time is based on a relative scale and requires a baseline value for comparison due to inconsistencies between the source and formulation of the activator being used. It is usually ordered in situations where the partial thromboplastin time test may take an excessive amount of time to process or is not clinically useful. Prolongation of the ACT may indicate a deficiency in coagulation factors, thrombocytopenia, or platelet dysfunction. Clotting time measurements can be affected by drugs such as warfarin, aprotinin, and GpIIb/IIIa inhibitors, and physiologic disturbances such as hypothermia, hypervolemia, and hypovolemia.
