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Lab Dept:
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Coagulation
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Test Name:
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INHIBITOR SCREEN
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General Information
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Lab Order Codes:
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PTTI
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Synonyms:
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Factor VIII Inhibitor Screen; Factor IX Inhibitor Screen; PTT Inhibitor/Inactivator; Circulating Anticoagulant
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CPT Codes:
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85335 – Factor inhibitor test
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Test Includes:
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Pre and post 2 hour incubation of patient’s plasma with normal plasma as required
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Logistics
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Test Indications:
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Detection of circulating anticoagulants as may occur in multiple-transfused, factor-deficient patients, as associated with multiple myeloma, lupus, rheumatoid arthritis, ulcerative colitis, postpartum complication and other complications
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Lab Testing Section:
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Coagulation - Sendouts
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Referred to:
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Fairview University Medical Center
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Phone Numbers:
Minneapolis:
Saint Paul:
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612-813-6280
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651-220-6550
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Test Availability:
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Daily, 24 hours
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Turnaround Time:
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1 – 4 days; test set up 1 – 2 times/week
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Special Instructions:
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Indicate which factor inhibitor is suspected. No heparin can be present in the specimen. Indicate on the floor collected request form if the patient is receiving Coumadin® therapy.
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Specimen
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Specimen Type:
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Whole blood
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Container:
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Light Blue top (Buffered Na Citrate 3.2%) tube
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Draw Volume:
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8.1 mL blood in 3 – 2.7 mL tubes (Minimum: 5.4 mL in 2- 2.7 mL tubes)
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Processed Volume:
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Specimen will be processed by reference lab facility.
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Collection:
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Do Not use the first 2 mL of blood collected.
If the patient’s hematocrit is >55%, contact laboratory to obtain a special tube.
Mix thoroughly by gentle inversion.
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Special Processing:
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Lab Staff: Do Not process. Send in original Vacutainer® tube. Ship at room temperature. Must arrive at reference lab within 24 hours of collection.
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Patient Preparation:
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Coumadin® therapy should be discontinued for 2 weeks prior to testing. Heparin therapy should be discontinued 2 days prior to collection of specimen.
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Sample Rejection:
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Improper tube, Clotted samples, Underfilled tubes, Overfilled tubes, Mislabeled or unlabeled specimens
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Interpretive
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Reference Range:
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No circulating anticoagulant identified
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Critical Values:
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N/A
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Limitations:
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Accurate quantitation of inhibitor may not be possible if patient is or has been receiving replacement or anticoagulant therapy.
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Methodology:
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Serial dilutions of patient’s plasma with normal plasma incubated at room temperature and at 37ºC for 2 hours followed by PTT.
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References:
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Fairview University Medical Center Laboratory Web Page http://labguide.fairview.org/diagnostic.asp
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Harmening DH (1997) Clinical Hematology and Fundamentals of Hemostasis
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Updates:
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5/25/2010: Tubing patient specimens is no longer prohibited.
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