Activated Partial Thromboplastin Time (APTT)

Possible interpretation of the results

The extension of aPTT is related to:

• All congenital deficits (including hemophilia A and B, von Willebrand disease);
• Thrombin inhibitors (hirudin, argatroban);
• Streptokinase;
• Urokinase;
• Oral anticoagulant therapy;
• Vitamin K deficiency;
• Malnutrition;
• Intravascular coagulation syndrome;
• The presence of fibrin degradation products;
• The presence of circulating factor-specific anticoagulants;
• Nonspecific - Lupus anticoagulants.

• Normal PT (prothrombin time), prolonged aPTT: Deficiency of precalicrin or one of VIII, IX, XI and / or XII factors is likely.
• Prolonged PT, normal aPTT: Possible factor VII deficiency. Nutritional or therapeutic deficiency of vitamin K-dependent factors can sometimes lead to prolonged PT and normal aPTT.
• Prolonged PT and aPTT: Deficiency of factor I, II, V or X is likely.

The reduction in aPTT is related to:

• Increased levels of one factor, most often factor VIII;
• Common neoplasms (except when the liver is damaged);
• Severe bleeding;
• Early stage of DIC.

Prolonged aPTT indicates hemorrhagic disease, while reduced aPTT has been found to be an independent predictor of death at high risk of thrombosis and bleeding.

aPTT depends on the age of the patient: in infants the upper limit of aPTT extends to 55 s and gradually decreases to the adult level by 6 months; Prolonged values ​​of aPTT in healthy children are caused by a mild deficiency of several coagulation proteins. Even in the elderly aPTT may be reduced.