Description
Overview: The Activated Partial Thromboplastin Time (APTT) test evaluates the functionality of the intrinsic and common pathways of the coagulation cascade. This is a series of reactions in your body that leads to the formation of a blood clot. The test measures the number of seconds it takes for a clot to form in a blood sample after specific reagents are added.
Clinical Significance:
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Bleeding Disorders: A prolonged (longer than normal) APTT can indicate a deficiency in certain clotting factors (such as Factor VIII in hemophilia A or Factor IX in hemophilia B) or the presence of an inhibitor.
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Clotting Disorders: It is used to investigate the cause of unexplained blood clots (thrombosis).
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Medication Monitoring: The test is essential for monitoring patients on unfractionated heparin therapy to ensure their dosage is safe and effective. It is generally not used to monitor low-molecular-weight heparin or warfarin (which is monitored with the PT/INR test).
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Pre-surgical Screening: It may be ordered before surgery to assess the risk of excessive bleeding.
When is this test recommended?
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To investigate unexplained or prolonged bleeding, such as frequent nosebleeds, heavy menstrual periods, or easy bruising.
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To monitor heparin therapy.
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As part of a pre-surgical evaluation.
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To screen for antiphospholipid syndrome, an autoimmune disorder that can cause inappropriate blood clots.
Sample Requirements:
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Specimen: Plasma.
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Container: Light Blue Top Tube (Sodium Citrate).
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Crucial Handling: The tube must be filled completely to the marked fill line to ensure the correct 9:1 ratio of blood to anticoagulant. An underfilled tube can lead to falsely prolonged results and may be rejected by the lab.
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Preparation: No fasting is typically required, but you should inform your doctor of any medications you are taking, especially blood thinners.
