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:
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.
Clotting Disorders: It is used to investigate the cause of unexplained blood clots (thrombosis).
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).
Pre-surgical Screening: It may be ordered before surgery to assess the risk of excessive bleeding.
When is this test recommended?
To investigate unexplained or prolonged bleeding, such as frequent nosebleeds, heavy menstrual periods, or easy bruising.
To monitor heparin therapy.
As part of a pre-surgical evaluation.
To screen for antiphospholipid syndrome, an autoimmune disorder that can cause inappropriate blood clots.
Sample Requirements:
Specimen: Plasma.
Container: Light Blue Top Tube (Sodium Citrate).
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.
Preparation: No fasting is typically required, but you should inform your doctor of any medications you are taking, especially blood thinners.
