Factor VIII Activity

Also known as: Antihemophilic Factor (AHF)

Clinical Use

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

Not provided.

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.

Test Details

Methodology

Automated Analyzer (Coagulation)

Biomarkers

Factor VIII

Analyte

Factor VIII Activity

Concentration / Level • Quantitative (Continuous) (e.g., copies/mL, % expression)

LOINC Codes

Order Codes

3209-4 - Fact VIII Act/Nor PPP

Result Codes

3209-4 - Fact VIII Act/Nor PPP

Result Turnaround Time

2-3 days

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.