Factor VIII Activity, Clotting (347)
Also known as: Hemophilia A, Procoagulant Factor 8, Hemophiliac Factor, Antihemophilic Factor, Factor VIII Functional
Use
Measurement of Factor VIII coagulant activity aids in evaluating coagulation function. The test is used in the diagnostic evaluation of suspected Hemophilia A and for investigation of prolonged activated partial thromboplastin time (aPTT). Factor VIII is an acute-phase reactant influenced by stress, activity, or contraceptive use, and levels may be normal in some carriers or elevated in non-hemophilia conditions.
Special Instructions
Whole blood must be processed promptly into platelet‑poor plasma, frozen and shipped. Processing requires centrifugation within 60 minutes, double spin to achieve platelet‑poor plasma (<10,000 platelets/µL), immediate freezing, and use of a light blue (sodium citrate) tube. Do not refrigerate whole blood prior to processing to avoid cryoprecipitate formation.
Limitations
Specimens that are hemolyzed or thawed, or whole blood stored refrigerated prior to processing, may yield falsely low results. Factor VIII levels are influenced by acute‑phase reactions and are not reliable for carrier detection in females; genetic testing is recommended for that purpose. Inhibitors such as lupus anticoagulant or drug interferences may affect activity measurement.
Methodology
Immunoassay (Other)
Biomarkers
Result Turnaround Time
2-4 days
Related Documents
For more information, please review the documents below
Specimen
Plasma
Volume
1 mL platelet‑poor plasma
Minimum Volume
0.5 mL platelet‑poor plasma
Container
Light Blue (Sodium Citrate) tube
Collection Instructions
Centrifuge within 60 minutes, double spin to platelet‑poor plasma (<10,000/mcL), freeze immediately, send frozen
Causes for Rejection
Hemolysis; thawed specimens
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | Unacceptable |
| Refrigerated | Unacceptable |
| Frozen | 30 Days |
Other tests from different labs that may be relevant