Partial thromboplastin time

The Partial thromboplastin time ( PTT, partial thromboplastin time English, nor aPTT, activated partial thromboplastin time) is a test to check the intrinsic coagulation system. It is an important control parameter in a heparin or thrombolytic therapy and for the detection of coagulation disorders.

To distinguish them is by the thromboplastin time (PT ) ( without the " partial" - measures the extrinsic clotting) and of the plasma thrombin (PTZ) (insulated test the common final pathway ).

Implementation

To measure the PTT clotting by the addition of phospholipids (deprecated also: Partial thromboplastin or platelet factor 3, a protein-free phospholipid ) is in the laboratory previously anticoagulated citrated blood, a surface-active substance set in motion again ( eg kaolin ) and calcium ions and determined the time until the occurrence of coagulation.

The normal value is in healthy humans at 20 to 38 seconds.

The PTT is extended, inter alia, at

• A lack of clotting factors I, II, V, VIII (hemophilia A) and IX (hemophilia B), X, XI, XII, HMWK, and prekallikrein
• Heparin therapy
• Presence of some forms of von Willebrand 's disease
• Lupus anticoagulant

In contrast, differences in platelet counts do not affect the PTT because of, for example, platelet -derived platelet factor 3 is an extra added.

A shortened PTT is probably without clinical significance.