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HelpTest ID F8INH Factor VIII Inhibitor Evaluation
Useful For
Detecting the presence and titer of a specific factor inhibitor directed against coagulation factor VIII
Profile Information
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| F8A | Coag Factor VIII Activity Assay, P | Yes | Yes |
Reflex Tests
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| IBETH | Bethesda Units | No | No |
| F8IS | Coag Factor VIII Assay Inhib Scrn,P | No | No |
| CCCR | Special Coagulation Interpretation | 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 decreased, an inhibitor screen will be performed to look for specific factor VIII inhibition. If specific inhibition is apparent, the titer of the inhibitor will be determined.
Special Instructions
Method Name
F8A: Activated Partial Thromboplastin Clot-Based Assay
F8IS, IBETH: Clot-Based Assay
Reporting Name
Factor 8 Inhib ProfSpecimen Type
Plasma Na CitSee Coagulation Studies in Special Instructions.
Specimen Type: Platelet-poor plasma
Collection Container/Tube: Light-blue top (citrate)
Submission Container/Tube: Plastic vials
Specimen Volume: 3 mL in 3 plastic vials each containing 1 mL
Collection Instructions:
1. Specimen must be drawn prior to factor replacement therapy.
2. Spin down, remove plasma, and spin plasma again.
3. Freeze specimens immediately at ≤-40 degrees C, if possible.
4. Send specimens in the same shipping container.
Additional Information:
1. Double-centrifuged specimen is critical for accurate results as platelet contamination may cause spurious results.
2. If priority specimen, mark request form, give reason, and request a call-back.
3. Each coagulation assay requested should have its own vial.
Forms: If not ordering electronically, complete, print, and send a Coagulation Test Request Form (T753) with the specimen (http://www.mayomedicallaboratories.com/it-mmfiles/coagulation-test-request-form.pdf)
Specimen Minimum Volume
2 mL
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Plasma Na Cit | Frozen | 14 days |
Clinical Information
Factor VIII 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
-Elderly nonhemophiliac 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 usually have normal or elevated factor VIII.*
*See Pediatric Hemostasis References in Coagulation Studies in Special Instructions.
FACTOR VIII INHIBITOR SCREEN
Negative
BETHESDA TITER
0 Units
Cautions
This test is not useful for detecting the presence of inhibitors directed against other clotting factors and will not detect the presence of lupus anticoagulants.
If presence or type of inhibitor is unknown, PROCT / Prolonged Clot Time Profile or LUPPR / Lupus Anticoagulant Profile should be ordered.
Occasionally, a potent lupus-like anticoagulant may cause false-positive results for a specific factor inhibitor (eg, factor VIII or IX). See preceding caution statement.
Day(s) Performed
Monday through Friday; Varies
Report Available
2 daysPerforming Laboratory
Mayo Medical Laboratories in Rochester
CPT Code Information
85240-Factor VIII activity assay
85335-Bethesda titer (if appropriate)
85335-Factor VIII inhibitor screen (if appropriate)
85390-26-Special coagulation interpretation (if appropriate)