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UW Health SMPH
American Family Children's Hospital

UW Hospital and Clinics Lab Test Directory

Test Name: Factor Inhibitor Assay

Test Code(s): FIA / GM1335

CPT Code(s): 85335

Test Description: Test Component:

Factor Inhibitor assays are available when a specific inhibitor strength needs to be assessed. A factor activity level will be performed prior to the Factor Inhibitor Assay.

Methodology: Bethesda Inhibitor Assay

Clinical Significance: The assay is used to determine the titer of inhibitor to specific factors.

Days Performed: Mon-Fri, dayshift - day varies. Specimens are accepted at any time. Testing required during off hours must be approved by a Coagulation physician. Call 263-5005 before collection.

Turnaround Time: Stat: 1 working day.
Routine: 4 - 7 working days.

Specimen Requirements

Specimen: Blood

Patient Preparation: Patient MUST be off direct thrombin inhibitor for 24 hours and off heparin for 72 hours prior to blood collection.

Collection Instructions: Please note factor to be assayed. Do NOT draw through a line containing heparin. The venipuncture MUST be atraumatic to avoid hemolysis and contamination with tissue factors and platelets. Tube must be allowed to fill completely.

Indicate if patient is receiving anticoagulant (warfarin/Heparin/ Vitamin K antagonist), direct thrombin inhibitor or fibrinolytic agent therapy and duration.

Collection Container: Preferred: Light blue top (3.2% NaCitrate)

Collection Volume: Preferred: Four full 3.5 mL tubes
Pediatrics: 2 full pediatric tubes filled to mark

Sample Analyzed: Plasma

Volume Required: Preferred: 5 mL
Pediatrics: 1.5 mL

Specimen Processing: Ultracentrifuge sample and label "ULT". If an ultracentrifuge is not available, centrifuge tube to obtain platelet poor plasma (platelet count should be 10 K/L or less). Separate plasma from cells and transfer to plastic tube and spin again. Transfer this plasma to clean plastic tube or vial. Indicate on tube "spun twice". Freeze plasma within 4 hours of collection at -20C or below.

Specimen Transport: Transport whole blood specimen at room temperature to UWHC Core Laboratory (B4/220) within 4 hours of collection. See "Specimen Processing" for instructions if transport criteria can not be met. Transport frozen plasma aliquot on dry ice to UWHC Core Laboratory (B4/220).

Unacceptable Criteria: Hemolyzed specimens, clotted specimens, partially filled tubes and whole blood specimens greater than 4 hours old when received by the laboratory are not acceptable.

Stability: Ambient: 4 hours on a spun tube
Refrigerated: Not acceptable
Frozen: 2 weeks at -20C; 6 months at -70C


Expected Results:

Age 1 year and up: Negative

Coagulation Factor Inhibitor Assay Bethesda

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