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APTT (Activated-Partial-Thromboplastin-Time)

About the test
What is this test done for?
APTT or activated partial thromboplastin time is a specialized blood test done for monitoring heparin (anticoagulant) therapy.
Why is it Done?
This is a specialized blood test done for checking the response to heparin therapy. This test is similar to PTT (partial thromboplastin time), but this is more sensitive then PTT. This test is used in conjunction with PT (prothrombin time) to measure how quickly blood clotting takes place.It is also useful in assessing
  • Bleeding problems
  • The dose of medicines that reduce the blood clotting (blood thinners), like heparin
  • Liver disease (due to diminished synthesis of clotting factors)
When should it be performed?
This test is performed
  • When the patient has
    • Unexplained bleeding or bruising
    • Thrombotic episodes or recurrent miscarriages
    • Abnormal clotting pattern
    • Easy bleeding from small injuries
  • To assess the effectiveness of drug therapy like heparin/warfarin
  • To evaluate the integrity of intrinsic pathway of blood clotting
  • Before surgeries, in patients who have history of profuse bleeding or easy bruising
  • As a part of an evaluation for lupus anticoagulant antibodies
How is it done
A blood sample will be collected from a vein in your arm. Fasting is not necessary
Normal, if readings are 30-40 seconds
  • Absence of bleeding/clotting anomaly
Prolonged, if readings are > 40 seconds
  • Congenital deficiency of clotting factors like factor VIII, IX, XI & XII, including hemophilia A & hemophilia B
  • Congenital deficiency of prekallikrein
  • Von Willebrand Disease
  • Liver cirrhosis
  • Vitamin K deficiency
  • DIC
  • Heparin therapy
  • Coumarin therapy
Shortened, if readings < 30 seconds
  • Early stage of DIC
  • Extensive cancer
  • Immediately after acute hemorrhage
Critical levels, if readings > 70 seconds
  • Spontaneous bleeding
  • Excessive drug therapy (heparin therapy)
Other Tests
  • Prothrombin time (PT) and PT INR
    • Increased PT or high levels of PT INR suggest bleeding disorder or liver cirrhosis or anticoagulant therapy like warfarin
  • Thrombin time testing
    • It is a blood test used as a screening test to assess function of fibrinogen
    • Abnormal readings (increased time) suggest fibrinogen abnormality, impairment of fibrin formation or thrombin inhibitory effect
  • Platelet counts
    • It is a routine blood test used to assess the amount of platelets present in the body
    • Abnormal readings (low platelets) suggest acute bleeding, impaired bone marrow function or infections like malaria or dengue
  • Fibrinogen testing
    • It is a specialized blood test done to assess fibrinogen levels in the blood
    • Low levels indicate liver failure, DIC, severe malnutrition, afibrinogenemia or hypofibrinogenemia
  • Bleeding time & clotting time
    • It is a routine blood test
    • It gives reading of how much time does it take for blood to clot and bleeding to stop
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