Activated partial thromboplastin time
The activated Partial Thromboplastin Time (aPTT) is the global test of the endogenous coagulation and primarily dependent of the factors in the intrinsic system (factor XII, Prekallikrein, high molecular kininogen, factor XI, factor IX, factor VIII, factor X, factor V and factor II). The factors XII and XI are activated by phospholipids, surface-active substances as kaolin, celite or ellagic acid and calcium ions. Hence, the intrinsic enzyme cascade is triggered and the time until formation of a fibrin clot is measured. The Lupus Anticoagulant causes unspecific prolongations of the aPTT. Reference values such as sensitivity to factor deficiency and anticoagulants are strongly reagent dependent and it is therefore always necessary to relate the results to the reference range of the laboratory in question.
The activated Partial Thromboplastin Time (aPTT) is the global test of the endogene coagulation and primarily dependent of the factors in the intrinsic system (factor XII, Prekallikrein, high molecular Kininogen, factor XI, factor IX, factor VIII, factor X, factor V and factor II).
Further the aPTT can be used for monitoring of therapy with unfractionated Heparin.
Lipidemia and faulty sample drawing technique can shorten the aPTT.
A prolonged aPTT may be caused by:
- Oral anticoagulants, heparin, hirudin, aprotinin;
- Taurolin infusion;
- Primary or secondary polycythemia caused by a misbalance in the citrate-plasma-relation
A shortened aPTT may be caused by:
- Ovulation inhibitors
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