Coagulation Factor VIII Activity Assay, Plasma
Use
This test is useful for diagnosing hemophilia A, diagnosing von Willebrand disease when measured with von Willebrand factor antigen and activity, diagnosing acquired deficiency states, investigating prolonged activated partial thromboplastin time, and monitoring infusions of factor VIII replacement during interventional procedures and prophylactic infusions. It is not useful for inferring carrier status in suspected female carriers of hemophilia A unless the activity is less than 50% of normal. Factor VIII is a coagulation cofactor in the intrinsic coagulation pathway, primarily synthesized in the liver. Congenital factor VIII deficiency causes hemophilia A, which occurs in 1 in 10,000 male births and is inherited in a recessive sex-linked manner on the X chromosome.
Special Instructions
Coagulation testing is complex and may require multiple assays and clinical correlation. It is recommended to consider ordering a Coagulation Consultation. Provide priority specimen details if applicable, including reason and request for callback. Special handling instructions include marking the request form for priority specimens and ensuring proper patient preparation to avoid anticoagulant therapy before collection.
Limitations
Factor VIII is a labile protein, and its activity can be spuriously decreased due to proteolytic inactivation or improper handling, even if frozen. Decreased results need correlation with clinical and laboratory information, and repeat testing may be necessary. Factor VIII activity is influenced by conditions such as pregnancy, hormone therapy, and stress, which may elevate levels. Proper specimen handling is critical to avoid false results, with specific collection and storage requirements including freezing immediately after collection.
New York Approved
Methodology
Other
Biomarkers
LOINC Codes
- 3209-4
- 3209-4
Result Turnaround Time
1-3 days
Related Documents
For more information, please review the documents below
Specimen
Plasma
Volume
1 mL
Minimum Volume
0.5 mL
Container
Light-blue top (3.2% sodium citrate) tube; Plastic vial for submission
Collection Instructions
Specimen must be collected prior to factor replacement therapy. Centrifuge, transfer all plasma into a plastic vial, and centrifuge plasma again. Aliquot plasma into a plastic vial leaving 0.25 mL in the bottom of the centrifuged vial. Freeze plasma immediately (no longer than 4 hours after collection) at -20 degrees C or ideally at or below -40 degrees C.
Patient Preparation
Patient must not be receiving Coumadin (warfarin) or heparin therapy.
Causes for Rejection
Gross hemolysis, gross lipemia, gross icterus
Stability Requirements
| Temperature | Period |
|---|---|
| Frozen | 14 days |