Factor VIII Activity

F8, Factor 8, Factor VIII, UOW1504

Factor VIII (8) activity is a PTT-based factor assay used for diagnosing acquired or congenital factor VIII deficiency (hemophilia A) and acquired or congenital von Willebrand disease when measured in combination with the von Willebrand factor antigen and VWF Activity. The factor VIII activity can also be used to monitor infusions of factor VIII replacement during procedures and prophylactic infusions.

Emicizumab (Hemlibra) will affect all PTT-based assays and will overestimate the factor concentrations. Certain extended half-life formulation of recombinant factor VIII may give unreliable results with various factor VIII assays.

3 mL or 5 mL Light Blue Citrate Tube

Plasma

The Laboratory MUST process specimen, within 4 hrs of blood collection.

MUST PROCESS WITHIN 4 HOURS OF COLLECTION
Platelet poor Coag Citrate Specimen processing:
1. Gently invert tube 2-3 times prior to placing in Centrifuge
2. Centrifuge Citrate whole blood at 4500 rpm for 10 minutes
3. Carefully pipette plasma, avoiding the platelet/buffy coat into a plastic vial
4. Centrifuge plasma at 4500 rpm for 10 minutes
5. Pipette the plasma to a plastic vial, leaving the bottom 0.25 mL undisturbed
6. Freeze plasma immediately and transport frozen. 

1 mL

Patients on hirudin (Refludan), bivalrudin (Angiomax), Dabigatran (Pradaxa), rivaroxaban (Xarelto), apixaban (Eliquis), edoxaban (Savaysa) and argatroban (Novastan) may show prolonged clotting times. This may cause an under-estimation of the factor concentrations.

Emicizumab (Hemlibra) will affect all PTT-based assays and will overestimate the factor concentrations - these patients should be monitored utilizing a chromogenic factor assay.

Certain extended half-life formulation of recombinant factor VIII may give unreliable results with various factor VIII assays.

Coagulation

Stago STA Clottable PTT-based Factor Assay

Monday - Friday

85240

Units: %

Yes

UW

3209-4