HealthFlex
×
  • Home
  • Immunology Book
  • Lab Tests
    • Hematology
    • Fluid analysis
    • CSF
    • Urine Analysis
    • Chemical pathology
    • Blood banking
    • Fungi
    • General pathology
    • Immune system
    • Microbiology
    • Parasitology
    • Pathology
    • Tumor marker
    • Virology
    • Cytology
  • Lectures
    • Bacteriology
    • Liver
    • Lymph node
    • Mycology
    • Virology
  • Blog
    • Economics and technical
    • Fitness health
    • Mental health
    • Nutrition
    • Travel
    • Preventive health
    • Nature and photos
    • General topic
  • Medical Dictionary
  • About Us
  • Contact

Coagulation:- part 4 – Partial Thromboplastin Time (PTT)

September 20, 2022HematologyLab Tests

Table of Contents

  • Partial Thromboplastin Time (PTT)
        • Sample
        • Indications for Partial Thromboplastin Time (PTT)
        • Pathophysiology of Partial Thromboplastin Time (PTT)
        • Heparin mechanism of action:
    • PTT is a one-stage test.
        • The normal value of Partial Thromboplastin Time (PTT)
        • Difference between PTT, APTT, and PT:
        • Abnormal PTT high level is because of:
        • Decreased PTT level:
        • Differential diagnoses of bleeding disorders:
      • Critical values:

Partial Thromboplastin Time (PTT)

Sample

  1. The blood sample is taken in the anticoagulant.
  2. The PTT blood sample is 1.8 ml of blood and anticoagulant (maybe ESR solution) 0.2 ml.
    • Blood 1.8 ml + 0.2 ml ESR solution.

Indications for Partial Thromboplastin Time (PTT)

  1. Used to monitor the heparin therapy and control its dose.
  2. It is part of the coagulation panel workup.
  3. It evaluates:
    1. Extrinsic Pathway.
    2. Common Pathway.
  4. Advised to evaluate abnormal bleeding.
  5. It is recommended before the surgery.
  6. It evaluates factors I, II, V, VIII, IX, X, XI, and XII (1, 2, 5, 8, 9, 10, 11, 12).

Pathophysiology of Partial Thromboplastin Time (PTT)

  1. To understand the coagulation mechanism, go through the following diagrams, which give the various coagulation factors and their role.
Blood coagulation process: Coagulation pathways

Blood coagulation process: Coagulation pathways

Summary of the coagulation pathways

Summary of the coagulation pathways

  1. Hemostasis and the coagulation process represent the hemostatic balance which is between the clotting factors and factors encouraging clot dissolution.
  2. The first reaction of the body is the constriction of the blood vessels. In small blood vessels, this constriction may be enough to control the bleeding.
  3. In large blood vessels, a clot is needed to stop bleeding. This process will be as follows:
    1. The First stage is the changes in the platelets.
    2. The next phase is called the intrinsic system.
    3. Factor XII and other proteins form the complex on the subendothelial collagen in the damaged blood vessels.
    4. Activated factor XIa is formed, and in turn, it activates factor IXa.
    5. Now complex forms consist of factors VIII, IX, and X.
    6. Activated factor Xa enters the common pathway.
Coagulation hemostasis mechanism

Coagulation hemostasis mechanism

    1. At the same time, the extrinsic system is activated.
    2. There is a complex formation between the tissue thromboplastin (Factor III) and factor VII. Activated factor VIIa forms.
    3. VIIa can directly activate factor X.
    4. VIIa can also activate factors IX and X.
    5. When activators are added to the PTT reagent to shorten the clotting time. This process is called activated partial thromboplastin time APTT.
      1. The blood for APTT will be drawn 30 to 60 minutes before the next dose of heparin.
      2. If APTT is <50 seconds, then the dose of heparin is increased.
      3. When APTT is >100 seconds, it indicates an overdose of heparin.
Partial thromboplastin time

Partial thromboplastin time

Heparin mechanism of action:

  1. Heparin inactivates prothrombin (Factor II) and will prevent the formation of thromboplastin.
  2. It will prolong the intrinsic clotting mechanism, which may be around 4 to 6 hours between two doses of heparin therapy.
  3. The dose of heparin can be monitored by PTT.

PTT is a one-stage test.

  1. PTT serves the same function as APTT, but APTT is more sensitive.
  2. PTT detects the intrinsic pathway deficiency of the thromboplastin system and the common pathway.
  3. PTT also finds a defect in the extrinsic pathway.
  4. PTT screens intrinsic pathways and tests for the adequacy of factors XII, XI, IX, and VIII.
Principle of PTT (Partial Prothrombin time)

Principle of PTT (Partial thromboplastin time)

The normal value of Partial Thromboplastin Time (PTT)

  • This is compared with the normal control, which may vary from lab to lab.
  • Mostly with control, maybe 25 to 35 seconds.
  • Another source = 30 to 45 seconds
  • Patient taking anticoagulant therapy level:
    • PTT level is 1.5 to 2.5 times the normal value.

Difference between PTT, APTT, and PT:

  1. APTT is actually PTT.
  2. An incomplete thromboplastin reagent and calcium are added to the patient’s plasma. The time necessary to form the fibrin clot is measured.
  3. The PTT reagent is only phospholipid platelets substitute without other components of thromboplastin.
  4. The PTT is useful in detecting intrinsic factors abnormality but is insensitive to heparin therapy.
  5. The APTT is sensitive to heparin therapy.
  6. The APTT is very sensitive to coagulation factors deficiency in the intrinsic system before the prothrombin to thrombin stage.
  7. APTT is also abnormal in prothrombin or fibrinogen deficiencies, but only when the defect is very severe.
  8. APTT is not sensitive to prothrombin abnormality as PT because the extrinsic thromboplastin used in PT is more powerful than the intrinsic system prothrombin activator complex generated by the APTT so that PT will detect even the small defect in the prothrombin.
  9. Platelet abnormalities don’t affect the APTT.

Effects of various anticoagulants on Partial thromboplastin test (PTT) :

Various anticoagulants Effects of various anticoagulants on PTT
Heparin Increased
Urokinase Increased
Streptokinase Increased
Aspirin Normal
Warfarin Normal
Dipyridamole Normal
Sulfinpyrazone Normal

Abnormal PTT high level is because of:

  1. Liver diseases like Cirrhosis.
  2. Vitamin K deficiency.
  3. Disseminated intravascular coagulopathy (DIC).
  4. Heparin therapy.
  5. Coumarin therapy.
  6. Factor XII deficiency.
  7. Malabsorption.
  8. Congenital factors are deficiencies as seen in:
    1. Von Willebrand’s disease.
    2. Hemophilia A and B.
    3. Hypofibrinogenemia.

Decreased PTT level:

  1. Early stages of DIC.
  2. Extensive cancers like ovarian, pancreatic, and colon.
partial thromboplastin time (PTT): APTT and PT interpretations

partial thromboplastin time (PTT): APTT and PT interpretations

Differential diagnoses of bleeding disorders:

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. Platelets 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

Critical values:

  • PTT = >100 seconds
  • APTT = >70 seconds
Possible References Used
Go Back to Hematology

Add Comment Cancel


  • Lab Tests
    • Blood banking
    • Chemical pathology
    • CSF
    • Cytology
    • Fluid analysis
    • Fungi
    • General pathology
    • Hematology
    • Immune system
    • Microbiology
    • Parasitology
    • Pathology
    • Tumor marker
    • Urine Analysis
    • Virology

About Us

Labpedia.net is non-profit health information resource. All informations are useful for doctors, lab technicians, nurses, and paramedical staff. All the tests include details about the sampling, normal values, precautions, pathophysiology, and interpretation.

[email protected]

Quick Links

  • Blog
  • About Us
  • Contact
  • Disclaimer

Our Team

Professor Dr. Riaz Ahmad Bhutta

Dr. Naheed Afroz Syed

Dr. Asad Ahmad, M.D.

Dr. Shehpar Khan, M.D.

Copyright © 2014 - 2023. All Rights Reserved.
Web development by Farhan Ahmad.