1101. Activated Partial Thromboplastin Time (APTT)

Activated partial thromboplastin time (APT) is a screening test that evaluates the blood coagulation system. This test can help identify coagulation factor dysfunctions and identify the underlying cause of both thrombosis and bleeding tendencies. This test is best evaluated in conjunction with other coagulation factors.

The activated partial thromboplastin time (APTT) is a sensitive test for assessing the intrinsic and common pathways of the coagulation cascade. APTT is determined by the duration of blood clot formation after plasma activation with a specific reagent simulating vascular injury. This test is an important tool in the diagnosis of coagulation disorders.

This test covers the activity of coagulation factors VIII, IX, XI, and XII, as well as prothrombin (factor II), V, and X, and is indispensable for:

• diagnosing congenital or acquired coagulopathies, such as hemophilia A or B;
• detecting antiphospholipid syndrome (e.g., lupus anticoagulant);
• monitoring treatment with unfractionated heparin;
• screening for bleeding risks before surgery.

An elevated APTT value indicates a reduced ability of the blood to clot (increased risk of bleeding), while a reduced value indicates a tendency towards thrombus formation.

When?

• For suspected hereditary bleeding disorders (hemophilia A, B, factor XI, XII deficiency).
• To assess hemostatic status before surgery.
• To monitor heparin therapy (intravenous or subcutaneous administration of unfractionated heparin).
• To screen for antiphospholipid syndrome.
• To identify the causes of spontaneous bleeding or thrombosis, particularly in patients with elevated ESR and edema.
• As part of the diagnostic process for hemophilia and von Willebrand disease.
• As part of the hemostasis assessment process for thrombotic complications (for screening for APS).
• To monitor postpartum complications.

Who?

• Patients with suspected hereditary bleeding disorders.
• Individuals preparing for surgery.
• Patients receiving heparin therapy.
• Individuals with suspected or diagnosed antiphospholipid syndrome.
• Patients with spontaneous bleeding or thrombosis, as well as with symptoms of inflammation (elevated ESR, edema).
• Pregnant women to assess the risk of bleeding or thrombosis and monitor postpartum complications.

• Venous blood

In order to exclude factors that may affect the test results, we recommend to follow the preparation rules: