APTT (Activated Partial Thromboplastin Time)

Partial thromboplastin time (PTT) and activated partial thromboplastin time (aPTT) are used to assess the same functions; however, in aPTT, an activator is added that speeds up the clotting time and results in a narrower reference range. The aPTT is considered a more sensitive version of the PTT and is used to monitor the patient’s response to heparin therapy.

Also Known asPTT, APTT, Partial Thromboplastin Time, Activated Partial Thromboplastin Time,
Test Purposemeasures the number of seconds it takes for a clot to form in a sample
Test PreparationsNo Need but Overnight Fasting Is Preferred
Test ComponentsAPTT, PTT
Specimen3 ML Whole Blood In 1 Blue Top (Sodium Citrate) Tube. Mix Thoroughly By Inversion.
Stability Room2 hours
Stability Refrigerated4 hours
Stability Frozen2 weeks
MethodPhoto-Optical Clot Detection
Download Report Download Report

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Purpose of the test (Indications)

  1. This is used for the diagnosis of bleeding disorders.
  2. APTT may be used in the patient to check treatment who are taking Heparin or other blood-thinning medicines.
  3. APTT measures the intrinsic system and common pathways.
  4. APTT detects the functioning of factors XII, XI, X, IX, VII, V, II, and I (12, 11, 10, 9, 7, 2, 1).
  5. For the diagnosis of Hemophilia and Christmas disease.

Why get Tested:

Your doctor might order this test to check for a bleeding disorder, such as hemophilia or von Willebrand disease. Symptoms of bleeding disorders include:

  • Bleeding or bruising easily
  • Blood clots that form when they shouldn’t
  • Blood in your poop or urine
  • Gums that bleed easily
  • Heavy menstrual periods in women.
  • nosebleeds
  • Swelling or pain in the joints

When To Get Tested?

When you have unexplained bleeding, inappropriate blood clotting, or recurrent miscarriages; sometimes when you are on standard heparin anticoagulant therapy; sometimes before a scheduled surgery

Sample Required:

  1. The blood is collected in an anticoagulant with a fixed ratio carefully.
    • Take 0.2 ml anticoagulant (ESR solution may be used) and 1.8 ml whole blood.
  2. The APTT sample may be taken 30 to 60 min before the next dose of Heparin.

Precaution for sample

  1. Plasma is stable for one hour at 4 °C and 28 days if frozen.
  2. Sample handling is very critical. If the ratio of blood and anticoagulant is not correct, then the results are false and raised.

Normal Values:

Source 1

  • Varies with the lab to lab.
  • Normal control is always run with the patient sample.
  • In general, 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 dose of Heparin may be increased.
    • When APTT is greater than 100 seconds is risky for the patient and there are chances for spontaneous bleeding.
    • Panic value Usually it is considered above 70 seconds.
  • Heparin effect is immediate and short-lived as compared to warfarin.

Source 2

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

Abnormal High Results Are Due To:

  • All congenital deficiencies of Intrinsic system coagulation factors.
  • Cirrhosis.
  • Disseminated intravascular coagulopathy (DIC ).
  • Factor XII deficiency.
  • Hemophilia A and B.
  • Hypofibrinogenemia.
  • Malabsorption.
  • Von Willebrand’s disease.
  • Vit K deficiency.
  • Fibrin breakdown products.
  • Leukemia.
  • Drugs.

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