Aptt

aPTT is the acronym for "activated partial thromboplastin time". The activated partial thromboplastin time is a modified form of PTT(partial thromboplastin time): in this case, the coagulation is activated in the laboratory by adding phospholipids.

The aPTT is not suitable for monitoring therapy with low-molecular-weight heparins (determination of anti-Xa activity is required here). The aPTT standard value is 27 to 35 seconds.

Acceptance conditions: Citrate blood

Examination of the endogenous coagulation system, suspected congenital or acquired deficiency of factors VIII, IX, XI, XII, HMW-kiniogen and prekallikrein, (preoperative screening), control of heparin therapy, argatroban and other direct thrombin inhibitors. aPTT is only of limited use for monitoring therapy with hirudin.

increased values (extension of the aPTT by)

• Congenital factor deficiency states: haemophilia A (factor VIII), haemophilia B (factor IX), von Willebrand syndrome (factor VIII); congenital deficiency of one of the factors I (fibrinogen), II, V, X, XI, XII, prekallikrein, HMWK; acquired factor deficiency states: severe liver dysfunction, autoimmune diseases with lupus inhibitors (antiphospholipid antibodies); inhibitors against factors
• UF-heparin, hirudin, LMW-heparin only in high dosage, ribaroxaban only slightly
• Fondaparinux and Danaparoid do not prolong the aPTT.
• Argatroban and Dabigatran prolong the aPTT.

lowered values (shortening of the aPTT) for:

• Acute-phase reaction, post-operative
• from the 3rd trimester of pregnancy until post partum, a shortening is considered an indication of complications

1. Graefe KH et al Anticoagulants In: Graefe KH et al (Eds) Pharmacology and Toxicology. Georg Thieme Publisher Stuttgart p.465