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Biochemistry

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.

Indication

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.

Interferences

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

Literature

1. Luxembourg B et al. Basiswissen Gerinnungslabor. Dtsch Ärzteblatt 104, C1260, 2007.
2. Cuker A, Ptashkin B, Konkle BA, Pipe SW, Whinna HC, Zheng XL, Cines DB, Pollak ES. Interlaboratory agreement in the monitoring of unfractionated heparin using the anti-factor Xa-correlated activated partial thromboplastin time. J Thromb Haemost 7, 80, 2009.
3. Erdinc S, Guler B. Effect of Tube Filling Order on Specific Coagulation Parameters in Healthy Subjects. Laboratory Medicine 38, 556-558, 2007.
4. Spahn R, Cerny V, Coats TJ, Duranteau J, Fernández-Mondéjar E, Gordini G, Stahel PF, Hunt BJ, Komadina R, Neugebauer E, Ozier Y, Riddez L, Schultz A, Vincent JL, Rossaint R. Management of Bleeding Following Major Trauma: a European Guideline. Crit Care 11, 414, 2007.
5. Smythe MA. Advances in Anticoagulation Management: The Role of Pharmacy, The Annals of Pharmacotherapy 41, 493-495, 2007.
6. McKenzie DB, Wong K, Edwards T. The Management of Patients With Mechanical Heart Valves and Intracerebral Haemorrhage. Br J Cardiol 15, 145-148, 2008.
7. Kamal AH, Tefferi A, Pruthi RK. How to interpret and pursue an abnormal prothrombin time, activated partial thromboplastin time, and bleeding time in adults. Mayo Clin Proc 82, 864-73, 2007.