Factor VIII Activity

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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

Forms & Requisitions

Outside clients should fill and submit Coagulation Patient Clinical History Form: Coagulation Patient Clinical History Form

Synonyms
F8, Factor 8, Factor VIII
Components

Interpretation

Method

Stago STA Clottable PTT-based Factor Assay

Reference Range
Units: %
Female Male
AgeRange AgeRange
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
Blood
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

Receiving Instructions

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.

Misc Sendout

Performance

Lab Department
Coagulation(COAG)
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.
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,
University of Washington Medical Center,
1959 NE Pacific street, Seattle, WA 98195

Billing & Coding

CPT Codes
85240
LOINC
3209-4
Interfaced Order Code
UOW1504
Interfaced Result Code
UOW1504