PT - APTT - FIB - TT
The prothrombin time is a coagulation screening test. It measures, as a whole, the activity of the coagulation factors II, V, VII, X and I.
A prolonged PT has been observed in the following clinical states: Congenital or acquired deficiencies of factor II, V, VII, X or fibrinogen; liver failure (cirrhosis, hepatitis); treatments with vitamin K antagonists; hypovitaminosis K: nutritional intake deficiency, disorders in absorption or metabolism of vitamin K (hemorrhagic disease of the newborn, cholestasis, treatment with antibiotics); fibrinolysis; DIC…
The PT is commonly used for monitoring vitamin K antagonist therapy because of its sensitivity to variations in the concentration of the vitamin K dependent factors II, VII and X. Consequently, the comparability of results of his test is essential for finding the therapeutical range. The use of the INR is recommended for the assessment of the vitamin K antagonist therapy in patients.
The Activated Partial Thromboplastin Time (APTT) is a general coagulation screening test of the coagulation factors XII, XI, IX, VIII, X, V, II and fibrinogen.
A prolongation of the APTT is encountered in the following situations:
– congenital deficiencies
– acquired deficiencies and abnormal conditions.
An increase of the fibrinogen level is found in cases of diabetes, inflammatory syndromes, obesity; a decrease of the fibrinogen level is observed in Disseminated Intravascular Coagulation (DIC), fibrinogenolysis. Furthermore, fibrinogen seems to be involved in the pathogenicity of thrombotic cardiovascular events.
The Thrombin Time (TT) is a rapid and simple test designed for the assessment of fibrin formation. The TT remains normal in deficiencies of factor XIII (fibrin stabilizing factor). The TT should first be performed before any other specific assays are attempted, when a prolongation of the overall tests (PT, APTT) cannot be explained.
Prolongation of the TT indicates:
– an abnormality of fibrinogen
– the presence of antithrombins