Factor VIII Activity
General Information
Lab Name
Factor VIII Activity
Lab Code
F8
Epic Name
Factor VIII Activity
Description
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.
Outside clients should fill and submit Coagulation Patient Clinical History Form: Coagulation Patient Clinical History Form
Synonyms
F8, Factor 8, Factor VIII
Interpretation
Method
Stago STA Clottable PTT-based Factor Assay
Reference Range
Units: %
| Female | Male | ||
|---|---|---|---|
| Age | Range | Age | Range |
| 0- | 50-200 | 0- | 50-200 |
Effective date: 08/17/2020
Interferences and Limitations
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.
Ordering & Collection
Specimen Type
Collection
3 or 5 mL BLUE TOP (CITRATE) tube
Forms & Requisitions
Outside clients should fill and submit Coagulation Patient Clinical History Form: Coagulation Patient Clinical History Form
Handling Instructions
The Laboratory MUST process specimen within 4 hrs of blood collection.
Quantity
requested: entire specimen
Processing
UW-MT/HMC: Take specimen to Coag lab for processing.
Outside Laboratory: Centrifuge for 10 minutes, remove plasma & re-spin plasma for another 10 minutes. Decant & freeze plasma (minimum 1.0 mL) @ -20°C to -80°C. Send frozen on dry ice.
Performance
LIS Dept Code
Coagulation (COAG)
Performing Location(s)
| HMC |
Coagulation
206-520-4600 325 9th Ave, Rm # GWH-47, Seattle, WA 98104-2420 |
|
|---|---|---|
| UW-MT |
Coagulation
206-520-4600 Clinical Lab, Room NW220, |
Frequency
Monday-Friday (8 am-3pm). Result end of day.
Available STAT?
Yes, Monday-Friday 8am-3pm. For other times, contact Lab Medicine Resident (LMR) for approval. If approved for after hours or weekend stat testing, LMR will notify UW-ML Coag lab at 206-598-6242 for samples collected at UW-ML and HMC Coag Lab at 206-744-3128 for samples collected at HMC and outside locations.
Billing & Coding
CPT codes
85240
LOINC
Interfaced Order Code
UOW1504
Interfaced Result Code
UOW1504