Question

Lab Tests

What do the results of a partial thromboplastin time mean?

A Answers (1)

  • AHealthwise answered

    Partial thromboplastin time (PTT) is a blood test that measures the time it takes your blood to clot.

    Normal

    The normal values listed here—called a reference range—are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.

      Partial thromboplastin time 1
    • Partial thromboplastin time (PTT):
    • 60–70 seconds

    • Activated partial thromboplastin time (APTT):
    • 30–40 seconds

    The heparin dose is changed so that the PTT or APTT result is about 1.5 to 2.5 times the normal value. 1

    Abnormal values
    • A longer-than-normal PTT or APTT can mean a lack of or low level of one of the blood clotting factors or another substance needed to clot blood. This can be caused by bleeding disorders, such as hemophilia or von Willebrand's disease.
    • A longer-than-normal PTT or APTT can be caused by liver disease, kidney disease (such as nephrotic syndrome ), or treatment with blood thinners, such as heparin or warfarin (Coumadin).
    • A longer-than-normal PTT may be caused by conditions such as antiphospholipid antibody syndrome or lupus anticoagulant syndrome. These conditions happen when the immune system makes antibodies that attack blood clotting factors. This can cause the blood to clot easily in veins and arteries.
    • The PTT can get longer when you are using heparin, so your PTT value needs to be closely checked. If you have a longer PTT, you may have a higher risk of bleeding.


    This information does not replace the advice of a doctor. Healthwise disclaims any warranty or liability for your use of this information. To learn more visit Healthwise.org

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