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Test ID: BIA Anti-Factor FIX
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Bethesda Inhibitor Assay Anti-Factor FIX
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Useful For
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To detect and determine the presence and titer of a specific factor inhibitor directed against coagulation factor IX.
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Method name and description
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Turbidimetric
Test is performed using Sysmex CS5100.The Bethesda assay is based on the ability of the patient’s plasma containing factor IX (or other factor) inhibitor to inactivate factor IX present in normal pooled plasma (NPP). Factor IX inhibitors can be measured immediately, there is no need for prolonged incubation >2hrs; the mixtures can be assayed after 5 min at 37ºC.
Inhibitors are measured in Bethesda Units (BU). One BU is defined as the quantity of inhibitor that neutralizes 50% of the factor IX in normal plasma.
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Clinical information
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Significant bleeding can result from the presence of a coagulation factor inhibitor and could be life-threatening. Whether the inhibitor is present due to hemophilia or of an acquired nature, it greatly complicates the treatment process of a decreased factor level. The titer of the inhibitor may determine the mode of treatment. Bethesda units are a standardization to give a uniform definition of an inhibitor.
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Specimen type / Specimen volume / Specimen container
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Plasma Na Cit. Platelet-poor plasma.
Specimen Volume:2.7 ml.
Container/Tube: Light-blue top (citrate)
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Collection instructions / Special Precautions / Timing of collection
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- Samples collected in HMC facilities MUST reach the coagulation laboratory within 1 hour of collection.
- Samples collected in non-HMC facilities / external clients: MUST reach coagulation laboratory within 1 hour of collection, if not applicable, centrifuge the whole blood and carefully remove the plasma (by pipette not by decanting) and send it in a temperature-controlled environment (18- 25 ºC) within 2 hours of centrifugation. If the transportation of the plasma can’t be within a maximum of 2 hours, prepare platelet-poor plasma as follows:
- Re-centrifuge the plasma again.
- Remove the top portion of plasma leaving approximately 250 ul in the bottom to discard.
- The double-centrifuged plasma should be aliquoted into labeled plastic tubes.
- Freeze immediately at -20 ºC or below
- Specimens must arrive frozen.
- If patient HCT is >55%, test will not be processed. The ordering Physician will be contacted to reorder the test and call the patient to go to Phlebotomy for recollection. Instruct the patient to inform the phlebotomy about his high HCT% , the phlebotomy will contact the lab to request a coagulation tube after adjusting amount of anticoagulant.
Note:
Collection of blood for coagulation testing through intravenous lines that have been previously flushed with heparin should be avoided, if possible. If the blood must be drawn through an indwelling catheter, possible heparin contamination and specimen dilution must be considered. When obtaining specimens from indwelling lines that may contain heparin, the line should be flushed with 5 mL of saline, and the first 5 mL of blood or 6-times the line volume (dead space volume of the catheter) be drawn off and not used for coagulation testing. For those specimens collected from a normal saline lock (capped off venous port) twice the dead space volume of the catheter and extension set should be discarded.
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Relevant clinical information to be provided
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Patient/family history of bleeding disorder. History of anticoagulant therapy. History of chronic diseases
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Storage and transport instructions
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Specimen Rejection Criteria
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Specimens with no label or missing required identification
Broken, leaking or contaminated specimen
Clotted samples
Under-filled or overfilled sample tubes.
Wrong sample container sample received
Improper specimen transport temperature (e.g. like specimens which are needed to be sent on ice)
Old specimen (test-dependent)
Grossly Hemolyzed sample (test-dependent)
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Biological reference intervals and clinical decision values
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Factors affecting test performance and result interpretation
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No interference up to:
Triglycerides 3028 mg/dL.
Hemoglobin 200 mg/dL.
Hemoglobin 48 mg/dL.
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Turnaround time / Days and times test performed / Specimen retention time
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For routine ordered test : 3 working days
For stat ordered test :
- During the Laboratory working hours from 0700 hours to 1500 hours (Sunday to Thursday): TAT is Within 8hrs.
- After duty hours, weekends and on holidays: TAT is within 12 hrs. with the following requirements:
- Laboratory should be notified by telephone about the sending of a STAT sample.
- The sample should be hand-delivered to the central processing area and requesting them to deliver it immediately to the hematology coagulation lab.
Test is done : Daily.
Specimen retention time: NA
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