Activated Partial Thromboplastin Time (APTT)
Why this test?
- To determine the patient's tendency to bleeding (as part of preoperative procedures).
- For the diagnosis of hemophilia.
- For the purpose of monitoring heparin-anticoagulant therapy.
- For the diagnosis of deep hypofibrinogenemia, dysfibrinogenemia and fibrin monomer polymerization disorders.
In what cases is it prescribed?
- If the patient has bleeding or bruising of unknown origin, thromboembolism or diffuse intravascular coagulation, which can cause both bleeding and blood clots.
- When carrying out heparin therapy or when transferring a patient from heparin therapy to long-term treatment with the use of warfarin.
- In the complex of preoperative examination to identify the body's propensity to bleeding, especially if the intended operation is associated with a large blood loss or earlier bleeding is indicated in the patient's clinical history. In the treatment of myocardial infarction.
Activated partial thromboplastin time (APT) characterizes the internal pathway of blood coagulation. APTC is the time during which a clot is formed in a blood plasma sample after adding special activators of this process to it. In this way, the degree of influence of blood coagulation factors on the formation of a thrombus is evaluated. The duration of APT depends on the level of high molecular weight kininogen, prekallikrein and coagulation factors XII, XI, VIII and is less sensitive to changes in the amount of factors X, V, prothrombin and fibrinogen. APTC is determined by the duration of blood clot formation after adding calcium and partial thromboplastin to the blood sample.
An increase in the duration of AChT is associated with an increased risk of bleeding, a decrease - with thrombosis. This indicator is used separately to control therapy with direct anticoagulants (heparin). What is the research used for: For the diagnosis of hemophilia. For the purpose of monitoring heparin-anticoagulant therapy.
For the diagnosis of deep hypofibrinogenemia, dysfibrinogenemia and fibrin monomer polymerization disorders. To determine the patient's tendency to bleeding (as part of preoperative procedures). What can affect the result: The presence of impurities of direct anticoagulants (in particular, heparin) in the blood sample High concentration of lipids (fats) in the blood, for example, after eating fatty food on the eve of the study Important notes: When very high doses of heparin are used, for example during open heart surgery, the test for AChT loses its sensitivity - thrombus formation is greatly reduced. APTT analysis is not prescribed as a regular screening test. It is needed if the patient's medical history indicates a hereditary tendency to thrombosis or hemophilia. Asymptomatic patients are often screened for APT before surgery, especially when their attending physician believes it will help determine the risk of excessive bleeding during surgery.