Routine tests of blood coagulation, such as the prothrombin time (PT), activated partial thromboplastin time (aPTT), and thrombin time (TT), are frequently ordered to assess clotting function in patients. Additional tests, such as anti-factor Xa activity, are sometimes used.
The nature of these tests and the evaluation of abnormal test results will be reviewed here. Additional topic reviews discuss the following:
●Overviews of the coagulation pathway and hemostasis (see "Overview of hemostasis" and "Vitamin K and the synthesis and function of gamma carboxyglutamic acid")
●Approach to patients with abnormal bleeding (see "Approach to the adult patient with a bleeding diathesis" and "Approach to the child with bleeding symptoms" and "Rare (recessively inherited) coagulation disorders" and "Coagulation abnormalities in patients with liver disease")
●Assessment of hemostasis preoperatively (see "Preoperative assessment of hemostasis")