APTT Test
1,250 Kshs | Home Collection Available
Synonyms
activated partial thromboplastin time
Purpose
The Activated Partial Thromboplastin Time (aPTT) test measures how long it takes for blood to clot, specifically evaluating the intrinsic and common coagulation pathways. It is commonly used to:
- Monitor heparin therapy, especially unfractionated heparin.
- Distinguish between specific inhibitors (like factor deficiencies) and nonspecific inhibitors, such as lupus anticoagulant.
- Screen for bleeding disorders, including hemophilia A and B.
- Evaluate unexplained prolonged clotting times before surgery or in patients with a history of bruising or bleeding.
The test can be combined with Prothrombin Time (PT/INR), Thrombin Time (TT), Fibrinogen Test, Lupus Anticoagulant Panel, Factor Assays, and Platelet Count. These tests together provide a comprehensive overview of a patient’s coagulation profile.
Patient Preparation
The patient should not be on anticoagulant therapy, avoid warfarin for two weeks before testing, and thrombin inhibitor therapies for three days before the test.
Samples
2 mL of plasma, frozen, collected in a blue top tube (sodium citrate). Citrated plasma samples should be collected by double centrifugation. Evacuated collection tubes must be filled to completion and mixed immediately by inversion to ensure a proper blood-to-anticoagulant ratio. Samples should be frozen.
Reference Range
30-40 secs.
Results Turnaround
2-3 days after receipt of samples.
Diseases / Diagnostic indicators
The aPTT test results help assess blood clotting efficiency and may point to various conditions:
Prolonged aPTT (above normal range):
Indicates a clotting disorder or the effect of anticoagulant therapy. Common causes include:
- Hemophilia A or B (deficiency in factor VIII or IX)
- von Willebrand disease (affects factor VIII stability)
- Heparin therapy (intentionally prolongs clotting to prevent thrombosis)
- Liver disease, lupus anticoagulant, or DIC (disseminated intravascular coagulation)
Normal aPTT:
- Suggests that the intrinsic and common clotting pathways are functioning properly. However, some mild bleeding disorders may still be present even with normal results.
Shortened aPTT (rare):
- It can occur due to acute phase reactions or inflammation, but it’s generally not clinically significant.
If the aPTT is prolonged, further testing such as mixing studies or specific clotting factor assays may be necessary to identify the exact cause. For more on Activated Partial Thromboplastin Time Test, read this study.