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Factor VIII Inhibitor, Chromogenic
Test Code15586
CPT Codes
85335
Preferred Specimen
2 mL frozen plasma collected in each of three separate sodium citrate (light blue-top) tubes
Minimum Volume
1 mL (x3)
Instructions
Platelet-poor plasma: Centrifuge light blue-top tube 15 minutes at approximately 1500 g within 60 minutes of collection. Using a plastic pipette, remove plasma, taking care to avoid the WBC/platelet buffy layer and place into a plastic vial. Centrifuge a second time and transfer platelet-poor plasma into a new plastic vial. Plasma must be free of platelets (<10,000/uL). Freeze immediately and ship on dry ice.
Transport Temperature
Frozen
Specimen Stability
Room temperature: Unacceptable
Refrigerated: Unacceptable
Frozen -20° C: 14 days
Frozen -70° C: 1 year
Refrigerated: Unacceptable
Frozen -20° C: 14 days
Frozen -70° C: 1 year
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Gross hemolysis • Grossly lipemic • Grossly icteric
Methodology
Chromogenic
Setup Schedule
Set up: Wed, Sun; Report available: 2-6 days
Reference Range
<0.6 BU/mL
Clinical Significance
Patients with severe and moderate hemophilia often need specific substitution therapy with plasma derived or recombinant Factor VIII concentrates. About 15-35% of hemophiliacs treated with FVIII concentrates develop specific alloantibodies against human FVIII (inhibitors). The development of functionally inhibiting alloantibodies in hemophilia represents a serious clinical problem. In some patients, infusion of excessive amounts of Factor VIII may be utilized to overcome the antibody. However, this may result in an increased titer of the inhibitor leaving the patient unresponsive to further treatment. Therefore, detection and quantitation of inhibitors is of great importance in the care of these patients.
In non-hemophiliacs, development of circulating FVIII inhibitors can lead to acquired hemophilia, a rare bleeding disorder with an incidence of 1 per 106 persons per year. Acquired hemophilia can develop in patients with immunologic disorders such as rheumatoid arthritis, postpartum women, and in older individuals with no underlying disease.
Inhibitors to Factor VIII have been denoted as high- or low-responses based on the amnestic response of the antibody to antigenic challenge. Alloantibodies, which demonstrate an increase in titer, have been termed high-response inhibitors while those that do not have been termed low-response inhibitors. An antibody which is persistently 5 Bethesda units per mL (BU/mL) despite repeated challenge with substitution factor concentrate should be termed as low-response inhibitor, whereas the term high-response inhibitor should be applied to cases where the inhibitory activities have been >5 BU/mL at any time.
Factor VIII Activity and Factor VIII Inhibitor give a quantitative value for inhibitor activity in the determination of treatment options and the Nijmegen gives a more accurate value to low titer inhibitors which impacts treatment options.
Unlike other tests which use human coagulation Factors IX and X, the reagents used in this test contain bovine Factors IX and X. In patients being treated with Emicizumab (Hemlibra), the drug will interact with activated Factor IX and Factor X, which will result in Factor X being activated in the absence of Factor VIII activity. This could result in a false negative result, as even in the presence of Factor VIII inhibitors Emicizumab will cause the coagulation cascade to proceed. Emicizumab does not interact with bovine factors therefore there is no risk of Emicizumab interference with this test.
In non-hemophiliacs, development of circulating FVIII inhibitors can lead to acquired hemophilia, a rare bleeding disorder with an incidence of 1 per 106 persons per year. Acquired hemophilia can develop in patients with immunologic disorders such as rheumatoid arthritis, postpartum women, and in older individuals with no underlying disease.
Inhibitors to Factor VIII have been denoted as high- or low-responses based on the amnestic response of the antibody to antigenic challenge. Alloantibodies, which demonstrate an increase in titer, have been termed high-response inhibitors while those that do not have been termed low-response inhibitors. An antibody which is persistently 5 Bethesda units per mL (BU/mL) despite repeated challenge with substitution factor concentrate should be termed as low-response inhibitor, whereas the term high-response inhibitor should be applied to cases where the inhibitory activities have been >5 BU/mL at any time.
Factor VIII Activity and Factor VIII Inhibitor give a quantitative value for inhibitor activity in the determination of treatment options and the Nijmegen gives a more accurate value to low titer inhibitors which impacts treatment options.
Unlike other tests which use human coagulation Factors IX and X, the reagents used in this test contain bovine Factors IX and X. In patients being treated with Emicizumab (Hemlibra), the drug will interact with activated Factor IX and Factor X, which will result in Factor X being activated in the absence of Factor VIII activity. This could result in a false negative result, as even in the presence of Factor VIII inhibitors Emicizumab will cause the coagulation cascade to proceed. Emicizumab does not interact with bovine factors therefore there is no risk of Emicizumab interference with this test.
