Mar 31, 2015




Clinical Hub,Tools & Resources,UWHC Lab Test Directory,Coagulation

Factor Inhibitor Assay

Factor Inhibitor Assay (GM1335) Coagulation Lab Test

Name: Factor Inhibitor Assay

Test Name: Factor Inhibitor Assay

Health Link Test Code: GM1335

LIS Test Code: FIA

CPT Code(s): 85335

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 Information:

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.

In-Lab Turnaround Time: 4 - 10 days.

Stat In-Lab Turnaround Time: 1 day.

Patient Preparation:

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

Specimen: Blood

Collection Container: Light blue top (3.2% NaCitrate)

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 Volume: Four full 3.5 mL tubes

Pediatric Collection Volume: 2 full pediatric tubes filled to mark

Stability Ambient:

4 hours on a spun tube

Stability Refridgerated:

Not acceptable

Stability Frozen:

2 weeks at -20°C; 6 months at -70°C

Sample Analyzed: Plasma

Testing Volume: 5 mL

Pediatric Testing Volume: 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/µL 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 -20°C or below.

Specimen Transport:

Transport whole blood specimen at room temperature to UWHC Hospital Laboratory 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 Hospital Laboratory.

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.


Age 1 year and up: Negative

Interpretation Type: Expected Results