Author: Prof. Dr. med. Peter Altmeyer

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Last updated on: 29.10.2020

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activated partial thromboplastin time

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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.

General information
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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

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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.

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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

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

Outgoing links (1)

Thromboplastin time partial;


Last updated on: 29.10.2020