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Activated Partial Thromboplastin Time (APTT), Partial thromboplastin time (PTT), Prothrombin time (PT)

March 19, 2025HematologyLab Tests

Table of Contents

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  • Activated Partial Thromboplastin Time (APTT)
        • What sample is needed for Activated Partial Thromboplastin (APTT)?
        • What are the precautions for Activated Partial Thromboplastin (APTT)?
        • What are the Indications for Activated Partial Thromboplastin (APTT)?
        • What is the principle of Activated Partial Thromboplastin (APTT)?
        • How will you define PTT and APTT?
        • Activated Partial Thromboplastin (APTT):
        • What is detected by the Activated Partial Thromboplastin (APTT)?
        • What are the theories of coagulation?
      • How is the coagulation cascade run?
        • What is the presentation of Bleeding disorders in various conditions?
    • Activated partial thromboplastin time (APTT):
        • How will you define APTT?
        • What reagents are used in APTT?
        • What is the significance of APTT?
        • What are the advantages of APTT?
        • What are the disadvantages of APTT?
    • Partial thromboplastin time (PTT):
        • How will you define PTT?
        • What are the indications for PTT?
        • What is the significance of PTT?
    • Prothrombin time (PT):
        • How will you define prothrombin time (PT)?
        • What are the indications for Prothrombin time (PT)?
        • What are the contents of prothrombin time (PT) reagents?   
        • What is the significance of prothrombin time (PT)?
      • What is the normal value of PTT and APTT
      • What are the causes of increased APTT value?
      • What are the PT and APTT levels in various diseases?
      • What is the value of these tests for laymen?
      • Questions and answers:

Activated Partial Thromboplastin Time (APTT)

What sample is needed for Activated Partial Thromboplastin (APTT)?

  1. The blood is carefully collected in an anticoagulant with a fixed ratio.
    • Take 0.2 ml anticoagulant (ESR solution may be used) and 1.8 ml whole blood.
  2. Draw blood from a 3.2% buffered citrated tube with a 9:1 = blood: citrate ratio.
    1. Citrate binds calcium and prevents coagulation.
  3. The APTT sample may be taken 30 to 60 minutes before the next dose of Heparin.

What are the precautions for Activated Partial Thromboplastin (APTT)?

  1. Plasma is stable for one hour at 4 °C and 28 days if frozen.
  2. Sample handling is very critical. If the blood and anticoagulant ratio is incorrect, then the results are false and raised.

What are the Indications for Activated Partial Thromboplastin (APTT)?

  1. APTT is used to monitor the heparin therapy.
  2. This is used for the diagnosis of bleeding disorders.
  3. APTT may be used to check treatment for patients taking Heparin or other blood-thinning medicines.
  4. APTT measures the intrinsic system and common pathways.
  5. APTT detects the functioning of factors XII, XI, X, IX, VII, V, II, and I (12, 11, 10, 9, 7, 5, 2, 1).
  6. For the diagnosis of Hemophilia and Christmas disease.
  7. APTT evaluates all coagulation factors except factors VII and XIII.
  8. PT is advised to monitor the extrinsic pathway.
    1. PT is also advised to monitor the warfarin therapy.
    2. PT also advised detecting factor VII deficiency.

What is the principle of Activated Partial Thromboplastin (APTT)?

  1. The PTT is a one-stage test.
  2. PTT evaluates Factor I (Fibrinogen), Factor II (prothrombin), Factor V, VIII, XI, X, XI, and XII (5, 8, 9, 10, 12) http://Blood Coagulation Factors.
  3. The partial thromboplastin time (PTT) and Activated Partial thromboplastin time (APTT) are for the same function, but APTT is a more sensitive version of PTT.

How will you define PTT and APTT?

The PTT is a one-stage clotting test.

  1. It screens for coagulation disorders.
  2. It can detect the deficiency of the intrinsic thromboplastin system.
  3. It also detects any deficiency of the extrinsic coagulation pathway.

Activated Partial Thromboplastin (APTT):

  1. APTT is PTT, but with the addition of an activator, the time for the clot formation is decreased.
  2. APTT is more sensitive than PTT.

What is detected by the Activated Partial Thromboplastin (APTT)?

  1.  Deficiency of the intrinsic pathway.
  2. Incubating anticoagulants.
  3. Monitor heparin therapy.
  4. It is part of the coagulation panel.

What are the theories of coagulation?

  1. To understand the basis of the PTT and APTT, we have to have the concept of the process of coagulation.
  2. In 1905 – 1906, P. Morowitz published the theory of blood coagulation. This was unchanged for 40 years. He divided coagulation into two phases.
Coagulation phases

Coagulation phases

  1. Modern theory divided this process into three stages.
Coagulation modern theory

Coagulation modern theory

How is the coagulation cascade run?

Coagulation pathways

Coagulation pathways

Coagulation pathway

Coagulation pathway

What is the presentation of Bleeding disorders in various conditions?

  1. Platelet disorders give rise to:
    1. Petechiae.
    2. There is bleeding from the mucous membranes,
  2. Coagulation factors deficiency  leads to:
    1. Deep hematomas.
    2. There is bleeding into the joints.
    3. There is hematuria.
  3. Bleeding disorders may be due to:
    1. Defects in the vascular system.
    2. Platelets disorders.
    3. Coagulation factors deficiency.
    4. Specific inhibitors.
    5. Fibrinolytic disorders.

Activated partial thromboplastin time (APTT):

How will you define APTT?

  1. APTT is very sensitive to coagulation factors deficiencies within the intrinsic pathway before the prothrombin to thrombin stage.
  2. APTT detects more deficiencies in the Intrinsic pathway.
  3. APTT is used to monitor heparin therapy.

What reagents are used in APTT?

  1.  Phospholipids substitute, activator.
  2. CaCl2 initiates fibrin clots.

What is the significance of APTT?

  1. PTT is used to detect coagulation disorder, specifically detecting the deficiency of the intrinsic thromboplastin system and finding the defect in the extrinsic pathway.
  2. APTT detects the intrinsic pathway and common pathway deficiency (XII, XI, IX, VIII, X, II, and I).
  3. PT and APTT abnormalities will tell us common pathways (X, V, II, and I).

What are the advantages of APTT?

  1. APTT reproducibility is adequate where there is <10% variation.
  2. Its reaction is less (30 to 50 seconds).
  3. It is easy to perform.
  4. It can be used in automation.

What are the disadvantages of APTT?

  1. Heparin above the required level causes APTT to be nonlinear and unreliable.
  2. Reagents from different companies produce different results, so it is not possible to compare the results.
  3. APTT is affected by warfarin.
APTT reaction

APTT reaction

Partial thromboplastin time (PTT):

How will you define PTT?

  1. PTT was useful in detecting intrinsic factor abnormalities, but it was relatively insensitive to the effect of heparin.
    1. However, APTT was sensitive to the heparin effect.
    2. The APTT was sensitive to coagulation factors deficiency within the intrinsic pathway before the prothrombin was converted to thrombin.

What are the indications for PTT?

  1. Detect the Intrinsic thromboplastin system.
  2. Detects Common Pathway.
  3. Factor I (fibrinogen), Factor II (prothrombin), V, VIII, IX, X, XI, and XII.
  4. Detects extrinsic coagulation.
  5. It is a one-stage clotting test.

What is the significance of PTT?

  1. In Hemophilia, PTT is prolonged.
  2. Coagulation factors are synthesized in the liver, so in liver diseases, they are decreased.
  3. PTT is prolonged in the abnormality of the deficiency of factors I, II, VII, XII, X, XI,  and XII.

Prothrombin time (PT):

How will you define prothrombin time (PT)?

  1. Prothrombin is a protein produced by the liver.
  2. Prothrombin production is dependent upon an adequate amount of vitamin K.
  3. It is one of the important screening tests for coagulation abnormality.

What are the indications for Prothrombin time (PT)?

  1. It measures potential defects in stage II of coagulation, extrinsic pathway.
  2. To monitor anticoagulant therapy with Coumadin.
  3. It is advised for coagulation disorder.
  4. It may be part of liver functions.

What are the contents of prothrombin time (PT) reagents?   

  1. The plasma of the patient.
  2. Complete tissue thromboplastin (this will activate the extrinsic coagulation system). 
  3. Phospholipids act as platelet substitutes.
  4. CaCl2.

What is the significance of prothrombin time (PT)?

  1. The PT test measures factors of extrinsic and common pathways (VII, X, V, II, and I).
  2. Factor VII is listed as the extrinsic system.
  3. Common pathways have the factors X, V, II, and I.
  4. PT  test is ideal to detect early vitamin K deficiency.
  5. PT also monitors oral anticoagulant therapy.
  6. In case of severe fibrinogen deficiency, it produces an abnormal PT test.
  7. PT does not detect deficiency of factors XII, XI, IX, VIII, or XIII.
Prothrombin time (PT) reaction

Prothrombin time (PT) reaction

Fibrin and clotting factors

Fibrin and clotting factors

What is the normal value of PTT and APTT

Source 1

  • Varies from lab to lab.
  • Normal control is always run with the patient sample.
  • In general, it is <35 seconds.
    • PTT: 60 to 70 seconds.
    • APTT: 30 to 40 seconds.
  • If APTT is less than 50 seconds, then the therapeutic goal is not achieved, and the Heparin dose may increase.
    • When APTT is greater than 100 seconds is risky for the patient, and there are chances of spontaneous bleeding.
  • Panic value Usually, it is considered above 70 seconds.
    • Heparin’s effect is immediate and short-lived as compared to warfarin.

Source 2

  • APTT = 30 to 40 seconds
  • PTT = 60 to 70 seconds
  • PT   = 11.0 to 13.0 seconds
  • Possible critical values
    • APTT = >70 seconds
    • PTT = > 100 seconds

What are the causes of increased APTT value?

  1. All congenital deficiencies (Intrinsic system coagulation factors).
  2. Cirrhosis.
  3. Disseminated intravascular coagulopathy (DIC ).
  4. Fibrin breakdown products.
  5. Factor XII deficiency.
  6. Hemophilia A and B.
  7. Hypofibrinogenemia.
  8. Malabsorption.
  9. Von Willebrand’s disease.
  10. Vit K deficiency.
  11. Fibrin breakdown products.
  12. Leukemia.
  13. Drugs.
  14. Heparin therapy.
  15. Warfarin therapy.
  16. In the case of streptokinase and urokinase.
  17. Circulating anticoagulant inhibitors. These may be specific for factor VIII.
    1. These are seen as anti-factor VIII and anti-factor IX in 5% to 10% of hemophilic patients.
    2. These are also in multiple plasma transfusions.
    3. Drug reactions.
    4. In the case of tuberculosis.
    5. In autoimmune diseases like SLE and rheumatoid arthritis.

What are the PT and APTT levels in various diseases?

APTT PT Platelets count Causes of bleeding disorders
  • Increased
  • Normal
  • Normal
  1. Heparin therapy
  2. Factor VIII, IX, and XI deficiencies
  3. Lupus anticoagulant
  4. von Willibrand’s disease
  • Normal
  • Increased
  • Normal
  1. Early coumadin therapy
  2. Factor VII deficiency or inhibitor
  3. Early vitamin K deficiency
  4. Early liver diseases
  • Increased
  • Increased
  • Normal
  1. Heparin therapy
  2. Coumadin therapy
  3. Malabsorption
  4. Liver diseases
  5. DIC (acute)
  6. Gall bladder diseases
  • Normal
  • Normal
  • Normal
  1. Chronic compensated DIC
  2. Von Willebrand’s disease
  3. Factor XIII deficiency
  4. Aspirin
  5. Uremia
  6. Fibrinogen disorder (dysfibrinogenemia)
  7. Vasculitis
  8. Scurvy
  9. Colonic carcinoma
  • Normal
  • Normal
  • Increased
  1. Proliferative disorders
  2. CML
  3. Polycythemia rubra vera
  4. Essential thrombocythemia
  • Normal
  • Normal
  • Decreased
  1. Hemodilution
  2. Platelet disorders (destruction)
  • Increased
  • Increased
  • Decreased
  1. Acute DIC
  2. Liver diseases
  3. Heparin-induced thrombocytopenia
  4. Hypersplenism
  5. Thrombotic thrombocytopenic purpura
  6. Hemolytic uremic syndrome

What is the value of these tests for laymen?

  1. This test is advised for patients treated with Heparin or blood-thinning drugs.
  2. PTT and INR also have been done in patients with blood-thinning drugs (warfarin).
  • For more information, please see PT and PTT.

Questions and answers:

Question 1: What will be the coagulation profile in factor VII deficiency??
Show answer
APTT and platelets are normal while PT is increased.
Question 2: What will be the coagulation profile in acute DIC?
Show answer
In acute DIC, PT and APTT are increased while platelets are decreased.

Possible References Used
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Comments

Coagulation:- part 7 – Blood Coagulation Factors and Their descriptions – Labpedia.net Reply
November 7, 2021

[…] and APTT are prolonged in factor V […]

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