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What is APTT test?

APTT, also known as activated partial thromboplastin time test, is a blood test that evaluates the time taken by the body to form blood clots. It helps in the evaluation of certain blood clotting factors and their functioning in the process of blood clot formation

Blood clotting is a process that helps in stopping the leakage of excessive blood from an injury or a cut. The moment the body tissues or blood vessels are injured, bleeding starts and, at the same time blood clotting (hemostasis) begins. Blood platelets clump together at the site of the injury and form a platelet plug so you don’t bleed out from minor injuries. On the surface of these platelets, different coagulation factors work together to form a fibrin clot, which acts like a mesh to stop bleeding. One such coagulation factor is thromboplastin.

  1. Why is APTT test performed?
  2. How do you prepare for APTT test?
  3. How is APTT test performed?
  4. What do APTT test results mean?

APTT test is neither a routine test nor a diagnostic test; it is used to check if further tests need to be done in a given condition. This test is performed along with other tests like prothrombin time (PT) when an individual shows the following symptoms:

  • A clot in a vein or an artery
  • Easy bleeding or bruising, which is sometimes unexplained (without any cause)
  • Chronic liver disease (liver cirrhosis) that has caused poor blood clotting
  • Acute episode of disseminated intravascular coagulation (DIC) that has caused an abnormal bleeding or clotting episode

APTT test is also performed in certain situations such as:

  • Recurrent miscarriages: To detect the presence of auto-antibodies such as lupus anticoagulant antibody, which is associated with clotting episodes, and recurrent miscarriages.
  • As a routine test: To monitor a patient on blood-thinning medications like heparin or when someone has switched from heparin to warfarin therapy; until the person is stabilized
  • As a part of pre-operative profile: To screen for bleeding disorders

APTT test helps in evaluating the integrity of the intrinsic and common pathways of blood coagulation, while PT aids in evaluating the extrinsic pathway. Thus, in most cases, both these tests are performed simultaneously to avoid misdiagnosis.

No special preparations are needed for this test; however, a high-fat meal should be avoided prior to blood collection as high-fat levels in blood (lipemia) are known to alter test results.

It is a simple test in which a blood sample is collected from a vein in your arm by inserting a needle into the vein.

Normal results

The normal range for activated partial thromboplastin time is 25 to 35 seconds, which indicates the absence of bleeding or clotting issues and proper functioning of the intrinsic coagulation pathway.

Abnormal results

Abnormal results are categorized as prolonged (> 40 seconds), shortened (< 30 seconds) and critical levels (> 100 seconds). Prolonged and critical levels indicate bleeding issues, while shortened levels indicate clotting issues.

More than 40 seconds of APTT or prolonged APTT indicates:

  • Congenital deficiency of clotting factors like factor VIII, IX, XI and XII, including hemophilia A and hemophilia B
  • Congenital deficiency of prekallikrein
  • Von Willebrand disease
  • Liver cirrhosis or chronic liver disease
  • Vitamin K deficiency
  • DIC
  • Heparin therapy

Less than 30 seconds of APTT or shortened APTT indicates:

  • Early stage of DIC
  • Extensive cancer
  • A recent episode of acute hemorrhage

More than 100 seconds of APTT (critical level) indicates:

  • Spontaneous bleeding
  • Excessive drug therapy (heparin or warfarin therapy)

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor.

APTT (Activated Partial Thromboplastin Time) Test की जांच का लैब टेस्ट करवाएं

APTT OR PTTK ( Activated  Partial Thromboplastin Time )

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  1. University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; Activated Partial Thromboplastin Clotting Time
  2. MedlinePlus Medical Encyclopedia: US National Library of Medicine; Partial thromboplastin time (PTT)
  3. Vandiver JW, Vondracek TG. Antifactor Xa levels versus activated partial thromboplastin time for monitoring unfractionated heparin.. Pharmacotherapy. 2012 Jun;32(6):546-58. doi: 10.1002/j.1875-9114.2011.01049.x. Epub 2012 Apr 24.
  4. World Federation of Hemophilia [internet]; ABOUT BLEEDING DISORDERS
  5. Lab Tests Online. Washington D.C.: American Association for Clinical Chemistry; Coagulation Cascade
  6. Pagana KD, Pagana TJ, eds. (2010). Mosby's Manual of Diagnostic and Laboratory Tests. 4th ed. St. Louis: Mosby Elsevier; Chap 2. Blood Studies
  7. Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests. 8th ed. Philadelphia: Lippincott Williams and Wilkins; chap 6. Overview of Chemistry Studies.
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  9. Armando Tripodi, Veena Chantarangkul, Ida Martinelli, Paolo Bucciarelli and Pier Mannuccio Mannucci. A shortened activated partial thromboplastin time is associated with the risk of venous thromboembolism. Blood 2004 104:3631-3634; doi: