APTT

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Activated Partial Thromboplastin Time (APTT)[edit | edit source]

The Activated Partial Thromboplastin Time (APTT) is a medical test that characterizes blood coagulation. It is used to evaluate the intrinsic pathway of coagulation and monitor patients on heparin therapy. The APTT is a critical component in the assessment of bleeding disorders and the management of anticoagulation therapy.

History[edit | edit source]

The APTT test was first developed in the 1950s as a means to evaluate the coagulation system. It has since become a standard test in clinical laboratories worldwide.

Physiology[edit | edit source]

The coagulation cascade is divided into the intrinsic, extrinsic, and common pathways. The APTT specifically assesses the intrinsic and common pathways. Factors involved in the intrinsic pathway include factor XII, factor XI, factor IX, and factor VIII. The common pathway involves factor X, factor V, prothrombin, and fibrinogen.

Procedure[edit | edit source]

The APTT test is performed by adding calcium and a phospholipid reagent to a plasma sample. The time it takes for a clot to form is measured in seconds. The normal range for APTT is typically between 30 to 40 seconds, but this can vary depending on the laboratory and the reagents used.

Clinical Significance[edit | edit source]

APTT is used to:

  • Diagnose bleeding disorders such as Hemophilia and von Willebrand disease.
  • Monitor patients on Heparin therapy.
  • Evaluate the coagulation status in patients with liver disease or vitamin K deficiency.

Interpretation[edit | edit source]

  • **Prolonged APTT**: May indicate deficiencies in factors VIII, IX, XI, or XII, the presence of inhibitors such as lupus anticoagulant, or the effects of heparin therapy.
  • **Shortened APTT**: Rarely clinically significant, but may occur in conditions of hypercoagulability.

Limitations[edit | edit source]

The APTT test can be affected by:

  • Improper sample collection or handling.
  • Presence of anticoagulants such as Warfarin.
  • Variability in reagents and equipment.

Also see[edit | edit source]



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