Activated Partial Thromboplastin Time (APTT)

SI UNITS (recommended)


* The SI unit is the recommended method of reporting clinical laboratory results

Partial Thromboplastin Time (PTT), aPTT; APTT
Units of measurement
s, sec

aPTT was first described by Langdell et al. It is employed to screen for abnormalities in the intrinsic (factors XII, XI, IX, VIII) and common coagulation pathway (Factors II, V, X and fibrinogen). aPTT may be ordered as part of a pre - surgical evaluation for bleeding tendencies, especially if the surgery carries an increased risk of blood loss or if the patient has a clinical history of bleeding. aPTT is moreover used for monitoring unfractionated heparin (UFH) therapy. A prolongation of the aPTT is also seen during oral anticoagulation therapy, after administration of thrombin inhibitors like hirudin, argatroban, or when circulating anticoagulants against a factor are present. Liver disease or consumptive coagulopathy may lead to prolonged aPTT results. Shortened aPTT results have been associated with hypercoagulability. The presence of non - specific inhibitors, such as lupus - anticoagulants, may prolong the aPTT.

SI units Conversion Calculator. Convert Activated Partial Thromboplastin Time (APTT) level to s, sec . Clinical laboratory units online conversion from conventional or traditional units to Si units. Table of conversion factors for Activated Partial Thromboplastin Time (APTT) unit conversion to s, sec .