Factor VIII Activity, Clotting
Test Code
Clinical Significance
Factor VIII Activity, Clotting - This test is useful to evaluate a prolonged aPTT. The most common form of hemophilia is caused by a deficiency of Factor VIII. Hemophilia A is an X-linked disorder affecting between 1 in 5,000 to 10,000 males. Borderline low Factor VIII activity can be seen in female carriers of the defective Factor VIII gene. Typically this test is combined with other screening tests (eg. von Willebrand factor, Ristocetin Cofactor Activity) to evaluate for the presence von Willebrand disease.
Anticoagulant interference: Expected impact by therapeutic levels (potential interference depends upon drug ...
Test Resources
Test Details
Methodology
Reference Range(s)
Alternative Name(s)
Preferred Specimen(s)
1 mL frozen platelet-poor plasma collected in 3.2% sodium citrate (light blue-top) tube
Minimum Volume
0.5 mL
Collection Instructions
Platelet-poor plasma: Centrifuge light blue-top tube for 15 minutes at approximately 1500 g within 60 minutes of collection. Using a plastic pipette, remove plasma, taking care to avoid the WBC/platelet buffy layer and place into a plastic vial. Centrifuge a second time and transfer platelet-poor plasma into a new plastic vial. Plasma must be free of platelets (<10,000/mcL). Freeze immediately and ship on dry ice.
Note: Storage of whole blood at refrigerated temperatures prior to processing may lead to cryoprecipitate formation and falsely low Factor VIII and von Willebrand Factor studies.
Transport Container
Transport tube
Transport Temperature
Frozen
Specimen Stability
- Room temperature: Unacceptable
- Refrigerated: Unacceptable
- Frozen: 30 days
Reject Criteria
Hemolysis • Received thawed
Setup Schedule
Note: Storage of whole blood at refrigerated temperatures prior to processing may lead to cryoprecipitate formation and falsely low Factor VIII and von Willebrand Factor studies.
Refrigerated: Unacceptable
Frozen: 30 days