Factor VIII Activity
Also known as: Antihemophilic Factor (AHF)
Use
Used in the evaluation of an isolated prolonged aPTT. Diagnosis of hemophilia A and as an aid in the diagnosis of von Willebrand factor (vWF) deficiency6-9
Special Instructions
If the patient's hematocrit exceeds 55%, the volume of citrate in the collection tube must be adjusted. Refer to Coagulation Collection Procedures for directions. Ideally, the patient should not be on anticoagulant therapy. Avoid warfarin therapy for two weeks and heparin, direct Xa, and thrombin inhibitor therapies for about three days prior to testing.
Limitations
Factor VIII is an acute phase reactant and can be elevated in various clinical conditions, affecting the accuracy of hemophilia diagnosis. Factor VIII levels should not be used to determine the carrier status of females; genetic testing is recommended. Factor VIII inhibitors can result in low levels, and a lupus anticoagulant may cause spuriously low factor VIII activity; chromogenic factor VIII activity is recommended in this case. Direct Xa or thrombin inhibitor therapy may cause factitiously low results.
Methodology
Automated Analyzer (Coagulation)
Biomarkers
LOINC Codes
- 3209-4
- 3209-4
Result Turnaround Time
2-3 days
Related Documents
For more information, please review the documents below
Specimen
Plasma
Volume
1 mL
Minimum Volume
Not provided
Container
Blue-top (sodium citrate) tube
Collection Instructions
Blood should be collected in a blue-top tube containing 3.2% buffered sodium citrate. Evacuated collection tubes must be filled to completion to ensure a proper blood-to-anticoagulant ratio. Mix immediately by gentle inversion six times.
Patient Preparation
Ideally the patient should not be on anticoagulant therapy. Avoid warfarin (Coumadin®) therapy for two weeks prior to the test and heparin, direct Xa, and thrombin inhibitor therapies for about three days prior to testing.
Storage Instructions
Freeze.
Causes for Rejection
Severe hemolysis; improper labeling; clotted specimen; specimen diluted with IV fluids; samples thawed in transit; improper sample type; sample out of stability.
Stability Requirements
| Temperature | Period |
|---|---|
| Frozen | 28 days |