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HelpTest Code LAB3700 Factor 8 Assay
Clinical System Name
Factor 8 Assay
Description
The quantitation of factor VIII in a patient's plasma can determine the presence and severity of factor VIII deficiency. It can be used to monitor treatment for hemophilia patients, and also used as part of the evaluation of Von Willebrands disease. Conversely elevated levels of Factor VIII is associated with mildly to moderately increased risk of venous thromboembolism.
Sample Requirements
Specimen: Whole Blood
Container(s): Lt Blue/Citrate
Required Vol: (1) 2.7 mL
Minimum Vol: (1) 1.8 mL
Preferred method of collection is venipuncture with vacuum fill. Test results are affected by incorrect blood volume. Use of a Vascular Access Device for the collection of coag testing is not recommended. Please review the Coagulation Lab Collection Job Aid for detailed instructions.
Processing Instructions: Main Campus
Deliver whole blood to Coag bench. Coag Technologist will process.
Reject due to: clotted, insufficient quantity (underfill), or improper collection (overfill).
Spin: Y
Aliquot: Y
Storage location: Core 14 Freezer ( -70 C).
Specimen should be centrifuged within one hour of collection. Transfer upper 3/4 layer of plasma to plastic tube affixed with large Epic aliquot label. Freeze one aliquot of plasma at -70 C. Preferred plasma volume: 1.0 mL, minimum plasma volume: 0.6 mL. Do not pool.
Processing Instructions: Offsite & Regional Clinics
Reject due to: clotted, insufficient quantity (underfill), or improper collection (overfill).
Spin: Y
Aliquot: Y
Storage location: -70 C (preferred) or -20 C.
Specimen should be centrifuged within one hour of collection. Double spin, transfer upper 3/4 layer of plasma to plastic tube affixed with large sample label. Freeze one aliquot of plasma at -70 C (preferred) or -20 C. Preferred plasma volume: 1.0 mL, minimum plasma volume: 0.6 mL. Do not pool.
Non-Children's Hospital Offsite collection: Ship completely frozen on dry ice.
Children's Hospital Regional Clinic collection: Ship completely frozen in frozen Nalgene Labtop cooler with ice pack inside an insulated soft cooler.
Stability
| Specimen Type | Temperature | Time |
|---|---|---|
| Citrated platelet-poor plasma | Room temp | ≤4 h |
| Refrigerated | N | |
| Frozen -20 C or -70 C | ≤3 m |
Performing Laboratory
Seattle Children's Laboratory
Department
Department: Coagulation
Phone Number: 206 987-2617 (Client Services)
Synonyms
LAB3700
Factor 8
Factor VIII
Factor VIII Activity
Availability
| STAT | Performed | TAT |
|---|---|---|
| Y* |
Wednesday and Friday |
1-7 d |
*See ordering note above for STAT requests.
Methodology
Method: Electromagnetic mechanical clot detection assay by STA-R MAX
Analytical Volume: 600 uL plasma
Limitations: Method is affected by insufficient quantity (underfill), improper collection (overfill), improper processing, and improper storage. High hematocrit greater than or equal to 56% requires a citrate adjusted tube.
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.
Reference Range
| % Activity | |
| Normal | 50 - 150 |
CPT Codes
85240
Critical Values
| % Activity | |
| Critical | < 30 |