- 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.