Clinical chemistry the denser blood cells and platelets to the bottom of the centrifuge tube, leaving the liquid serum fraction resting above the packed cells. This initial step before analysis has recently been included in instruments that operate on the "integrated system" principle. Plasma is in essence the same as serum, but is obtained by centrifuging the blood "without" clotting. Plasma is obtained by centrifugation "before" clotting occurs. The type of test required dictates what type of sample is used. A large medical laboratory will accept samples for up to about 700 different kinds of tests. Even the largest of laboratories rarely
Activated clotting time of 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 (PTT) 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 other drugs that such as Warfarin, aprotinin and GPIIb/IIIa inhibitors and may also be affected by physical perturbations to the body such as hypothermia, hypervolemia or hypovolemia. Activated clotting time Activated clotting time (ACT), also known