Factor VIII Chromogenic Bethesda Profile, for Patients on Emicizumab

TEST: 504722
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CPT: 85240(x2); 85335
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Special Instructions

Testing is performed at Esoterix Coagulation Laboratory (UY No. 301676).

For use in the confirmation and characterization of factor VIII inhibitors for patients on emicizumab therapy. Not intended for use with any other therapeutic.

Expected Turnaround Time

5 - 10 days

Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.

Related Documents

For more information, please view the literature below.

Procedures for Hemostasis and Thrombosis: A Clinical Test Compendium

    Specimen Requirements

    Specimen

    Citrated plasma, frozen

    Volume

    2 mL

    Minimum Volume

    1 mL

    Container

    Blue-top (sodium citrate) tube

    Collection

    Citrated plasma samples should be collected by double centrifugation. Blood should be collected in a blue-top tube containing 3.2% buffered sodium citrate.1 Evacuated collection tubes must be filled to completion to ensure a proper blood to anticoagulant ratio.2,3 The sample should be mixed immediately by gentle inversion at least six times to ensure adequate mixing of the anticoagulant with the blood. A discard tube is not required prior to collection of coagulation samples, except when using a winged blood collection device (ie, "butterfly"), in which case a discard tube should be used.4,5 When noncitrate tubes are collected for other tests, collect sterile and nonadditive (red-top) tubes prior to citrate (blue-top) tubes. Any tube containing an alternate anticoagulant should be collected after the blue-top tube. Gel-barrier tubes and serum tubes with clot initiators should also be collected after the citrate tubes. Centrifuge for 10 minutes. Use a second plastic pipette to remove the plasma, staying clear of the platelets at the bottom of the tube. Transfer the plasma into a Labcorp PP transpak frozen purple tube with screw cap (Labcorp No. 49482). Freeze immediately and maintain frozen until tested.

    Please print and use the Volume Guide for Coagulation Testing to ensure proper draw volume.

    Storage Instructions

    Freeze.

    Stability Requirements

    Temperature

    Period

    Frozen

    12 months

    Freeze/thaw cycles

    Stable x5

    Patient Preparation

    The patient should not be anticoagulated. Do not draw from an arm with a heparin lock or heparinized catheter.

    Causes for Rejection

    Patients on any therapy other than emicizumab therapy. Any sample other than citrated plasma (3.2% sodium citrate). Samples showing signs of activation, including the presence of fibrin clots, or received thawed.

    Test Details

    Use

    This assay is used to quantitate the titer of specific factor VIII antibodies in patients receiving emicizumab / Hemlibra®. Use of a standard, clot-based factor VIII test system will not accurately determine inhibitor titer due to interference from the therapeutic.

    Limitations

    Hemolysis, lipemia and icterus may interfere with this assay. Certain anticoagulant drugs (direct Xa inhibitors) may lead to an erroneously low factor activity and erroneously positive specific factor inhibitor results. Residual factor VIII activity could falsely lower the Bethesda titer although this is limited by heat-inactivation of the patient sample. Autoimmune inhibitors that demonstrate second order kinetics cannot always be accurately measured in the Bethesda titer system.

    Methodology

    The Nijmegen modification of the classic Bethesda inhibitor titration assay is used in a chromogenic factor VIII activity setting. Patient sample is heat-inactivated and clarified, then a serial dilution series is prepared in buffered normal plasma containing bovine serum albumin. A chromogenic factor activity is measured to determine residual activity and the inhibitor concentration is determined using an equation that relates the log % residual activity to inhibitor titer.

    Footnotes

    1. Adcock DM, Kressin DC, Marlar RA. Effect of 3.2% vs 3.8% sodium citrate concentration on routine coagulation testing. Am J Clin Pathol. 1997 Jan;107(1):105-110.8980376
    2. Reneke J, Etzell J, Leslie S, Ng VL, Gottfried EL. Prolonged prothrombin time and activated partial thromboplastin time due to underfilled specimen tubes with 109 mmol/L (3.2%) citrate anticoagulant. Am J Clin Pathol. 1998 Jun;109(6):754-757.9620035
    3. National Committee for Clinical Laboratory Standardization. Collection, Transport, and Processing of Blood Specimens for Coagulation Testing and General Performance of Coagulation Assays; Approved Guideline. 5th ed. Villanova, PA: NCCLS; 2008. Document H21-A5:28(5).
    4. Gottfried EL, Adachi MM. Prothrombin time and activated partial thromboplastin time can be performed on the first tube. Am J Clin Pathol. 1997 Jun;107(6):681-683.9169665
    5. McGlasson DL, More L, Best HA, Norris WL, Doe RH, Ray H. Drawing specimens for coagulation testing: Is a second tube necessary? Clin Lab Sci. 1999 May-Jun;12(3):137-139.10539100
    6. Adcock DM, Bethel MA, Macy PA. Coagulation Handbook. Aurora, CO: Esoterix-Colorado Coagulation; 2006.

    References

    Green D, Lechner K. A survey of 215 non-hemophilic patients with inhibitors to Factor VIII. Thromb Haemost. 1981 Jun 30;45(3):200-203.6792737
    Hay CR, Ludlam CA, Colvin BT, et al. Factor VIII inhibitors in mild and moderate-severity haemophilia A. UK Haemophilia Centre Directors Organisation. Thromb Haemost. 1998 Apr;79(4):762-766.9569189
    Kasper CK, Aledort L, Aronson D, et al. Proceedings: A more uniform measurement of factor VIII inhibitors. Thromb Diath Haemorrh. 1975 Nov 15;34(2):612.1198543
    Kasper CK. Laboratory tests for factor VIII inhibitors, their variation, significance, and interpretation. Blood Coagul Fibrinolysis. 1991;51(suppl 1):7.
    Triplett DA. Use of the dilute Russell viper venom time (dRVVT): its importance and pitfalls. J Autoimmun. 2000 Sep;15(2):173-178.10968905

    LOINC® Map

    Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
    504722 Emicizumab FVIII Inhib Panel 500666 Factor VIII Activity % 3209-4
    504722 Emicizumab FVIII Inhib Panel 500193 FVIII Chromogenic % 49865-9
    504722 Emicizumab FVIII Inhib Panel 504800 FVIII Chrom Nijmegen Bethesda CBU/mL 93450-5