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Test ID: F8INH    
Factor VIII Inhibitor Evaluation

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Useful For Suggests clinical disorders or settings where the test may be helpful

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

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

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 Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

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

Interpretation Provides information to assist in interpretation of the test results

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.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

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.

Clinical Reference Provides recommendations for further in-depth reading of a clinical nature

1. Kasper CK: Treatment of factor VIII inhibitors. Prog Hemost Thromb 1989;9:57-86

2. Peerschke EI, Castellone DD, Ledford-Kraemer M, et al: Laboratory assessment of FVIII inhibitor titer. Am J Clin Pathol 2009;131(4):552-558

3. Pruthi RK, Nichols WL: Autoimmune factor VIII inhibitors. Curr Opin Hematol 1999;6(5):314-322

Special Instructions and Forms Describes specimen collection and preparation information, test algorithms, and other information pertinent to test. Also includes pertinent information and consent forms to be used when requesting a particular test