Activated Partial Thromboplastin Time
The activated partial thromboplastin time (APTT) is used to evaluate all the clotting factors of the intrinsic pathway - except platelets - by measuring the time required for formation of a fibrin clot after the addition of calcium and phospholipid emulsion to a plasma sample. An activator, such as kaolin, is used to shorten clotting time.
Procedure and posttest care
Normally, a fibrin clot forms 21 to 35 seconds after addition of reagents. For a patient on anticoagulant therapy, ask the attending doctor to specify the reference values for the therapy being.
Prolonged APTT may indicate a deficiency of certain plasma clotting factors, the presence of heparin, or the presence of fibrin split products, fibrinolysins, or circulating anticoagulants that are antibodies to specific clotting factors
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