Activated Partial Thromboplastin Time

The Time required for the appearance of Fibrin strands following the mixing of Plasma with phospholipid Platelet substitute (e.g., crude Cephalins, Soybean Phosphatides). It is a test of the intrinsic pathway (factors VIII, IX, XI, and XII) and the common pathway (Fibrinogen, Prothrombin, factors V and X) of Blood Coagulation. It is used as a screening test and to monitor Heparin therapy.