Activated clotting timeActivated clotting time is a modification of the Lee–White clotting time with the addition of an activator, such as diatomaceous earth, Kaolin, or glass beads to whole blood to accelerate in vitro clotting by activating the contact system.
Unlike aPTT it has a range of sensitivity to high heparin levels that is linear and can be used to monitor patients during cardiopulmonary bypass and other interventional procedures in which high doses of heparin are used.
Other patient variables such as, the presence of acquired or congenital deficiency states and use of inhibitors such as antiphospholipid antibody and several patient variables of hypothermia after cardio pulmonary bypass can prolong the activated clotting time independent of the effects of heparin.