Factor VIII Chromogenic Activity
Also known as: Antihemophilic Factor (AHF)
Use
Used in the diagnosis of nonsevere hemophilia A.6, 7, 13 Useful in the accurate determination of factor VIII (FVIII) activity in the presence of a lupus anticoagulant or when certain modified recombinant FVIII replacement products are present. This assay can also be used in place of the one-stage (standard) FVIII activity assay for any indication.
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.
Limitations
Factor VIII is an acute phase reactant and can be elevated in various clinical conditions, affecting test accuracy in diagnosing hemophilia. Factor VIII levels should not be used to determine carrier status of females; genetic testing is advised. Inhibitors and lupus anticoagulant may affect results, and chromogenic factor VIII activity is recommended. Direct Xa inhibitor therapy may cause factitiously low results.
Methodology
Other
Biomarkers
LOINC Codes
- 49865-9
- 49865-9
Result Turnaround Time
3-5 days
Related Documents
For more information, please review the documents below
Specimen
Plasma
Volume
1 mL
Minimum Volume
0.5 mL
Container
Blue-top (sodium citrate) tube
Collection Instructions
Citrated plasma samples should be collected by double centrifugation. Blood should be collected in a blue-top tube containing 3.2% buffered sodium citrate. Fill evacuated collection tubes to completion. Mix immediately by gentle inversion at least six times.
Patient Preparation
Ideally the patient should not be on anticoagulant therapy. Avoid heparin and direct Xa inhibitor therapies for about three days prior to testing. Do not draw from an arm with a heparin lock or heparinized catheter.
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 |
|---|---|
| Room Temperature | 4 hours |
| Refrigerated | 4 hours |
| Frozen | 2 weeks |