activated partial thromboplastin time


activated partial thromboplastin time
(APTT) (aPTT) the period required for clot formation in recalcified blood plasma after contact activation and the addition of platelet substitutes (e.g., brain cephalin or similar phospholipids); used to assess the intrinsic and common pathways of coagulation. A prolonged aPTT can indicate a deficiency of a number of factors, including prekallikrein, high-molecular-weight kininogen, factors XII, XI, IX, VIII, X, V, and II, and fibrinogen.

Medical dictionary. 2011.