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Test Code 8INHE Factor VIII Inhibitor Evaluation, Plasma


Ordering Guidance


This test is for factor VIII inhibitors only. If the patient is known to have hemophilia A, this is the correct test to order. If the presence or type of inhibitor is unknown, first order APROL / Prolonged Clot Time Profile, Plasma. When screening studies are needed for patients with known hemophilia B, order 9INHE / Factor IX Inhibitor Evaluation, Plasma.



Shipping Instructions


Send all vials in the same shipping container.



Necessary Information


 



Specimen Required


Specimen Type: Platelet-poor plasma

Patient Preparation:

1. Patient must not be receiving Coumadin (warfarin) or heparin therapy

2. Fasting preferred

Collection Container/Tube: Light-blue top (3.2% sodium citrate)

Submission Container/Tube: Plastic vials

Specimen Volume: 3 mL in 3 plastic vials, each containing 1 mL

Collection Instructions:

1. Specimen must be collected prior to factor replacement therapy.

2. For complete instructions, see Coagulation Guidelines for Specimen Handling and Processing.

3. Centrifuge, transfer all plasma into a plastic vial, and centrifuge plasma again.

4. Aliquot plasma (1-2 mL per aliquot) into 3 separate plastic vials, leaving 0.25 mL in the bottom of centrifuged vial.

5. Freeze plasma immediately (no longer than 4 hours after collection) at -20° C or, ideally, at -40° C or below.

Additional Information:

1. Double-centrifuged specimen is critical for accurate results as platelet contamination may cause spurious results.

2. Each coagulation assay requested should have its own vial.


Useful For

Detecting the presence and titer of a specific factor inhibitor directed against coagulation factor VIII

 

This test is not useful for the detection of a lupus-like circulating anticoagulant inhibitor, a nonspecific circulating anticoagulant, or other inhibitors that are not specific for coagulation factors.

Disease States

  • Hemophilia A

Profile Information

Test ID Reporting Name Available Separately Always Performed
8INHT FVIII Inhib Profile Tech Interp No Yes
F8A Coag Factor VIII Activity Assay, P Yes Yes

Reflex Tests

Test ID Reporting Name Available Separately Always Performed
8AINH FVIII Inhib Profile Prof Interp No No
8BETH FVIII Bethesda Units, P No No
F8IS Coag Factor VIII Assay Inhib Scrn,P No No

Testing Algorithm

Testing begins with coagulation factor VIII activity assay with dilutions to evaluate assay inhibition; if the factor VIII activity assay is normal or increased, a technical interpretation will be provided.

 

If the factor VIII activity assay is decreased, an inhibitor screen will be performed at an additional charge to look for specific factor VIII inhibition and a professional interpretation will be provided. If specific inhibition is apparent, the titer of the inhibitor will be determined.

Method Name

F8A, F8IS, 8BETH: Optical Clot-Based

8INHT: Technical Interpretation

8AINH: Medical Interpretation

Reporting Name

Factor VIII Inhib Profile, P

Specimen Type

Plasma Na Cit

Specimen Minimum Volume

2 Plastic vials, each containing 1 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Plasma Na Cit Frozen 14 days

Reject Due To

Gross hemolysis Reject
Gross lipemia Reject
Gross icterus Reject

Clinical Information

Factor VIII (FVIII) inhibitors are IgG antibodies directed against coagulation FVIII that typically result in development of potentially life-threatening hemorrhage. These antibodies may develop in 1 of 4 different patient populations:

-Patients with congenital FVIII deficiency (hemophilia A) in response to therapeutic infusions of factor VIII concentrate

-Older nonhemophiliac adult patients (not previously factor VIII deficient)

-Women in postpartum period

-Patients with other autoimmune illnesses

Reference Values

FACTOR VIII ACTIVITY ASSAY

Adults: 55-200%

Normal, full-term newborn infants or healthy premature infants typically have levels greater or equal to 40%.*

*See Pediatric Hemostasis References in Coagulation Guidelines for Specimen Handling and Processing.

 

FACTOR VIII INHIBITOR SCREEN:

Negative

 

GENERAL FACTOR BETHESDA UNITS:
≤0.5 Bethesda Units

Interpretation

Normally, there is no inhibitor (ie, negative result).

 

If the screening assays indicate the presence of an inhibitor, it will be quantitated and reported in Bethesda (or equivalent) units.

Day(s) Performed

Monday through Friday

Report Available

1 to 3 days

Specimen Retention Time

7 days

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

This test has been modified from the manufacturer's instructions. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information

85390-Factor VIII Tech Interp

85240-Factor VIII activity assay

85335-Bethesda titer (if appropriate)

85335-Factor VIII inhibitor screen (if appropriate)

85390-Factor VIII Professional Interp (if appropriate)

LOINC Code Information

Test ID Test Order Name Order LOINC Value
8INHE Factor VIII Inhib Profile, P 96456-9

 

Result ID Test Result Name Result LOINC Value
F8A Coag Factor VIII Activity Assay, P 3209-4
8INHT FVIII Inhib Profile Tech Interp 69049-5

Forms

If not ordering electronically, complete, print, and send a Coagulation Test Request (T753) with the specimen.