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Lab Dept:
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Coagulation
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Test Name:
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HEPARIN ASSAY, UNFRACTIONATED
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General Information
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Lab Order Codes:
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HEPU (unfractionated heparin)
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Synonyms:
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Anti-Xa Assay
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CPT Codes:
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85520 – Heparin assay
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Test Includes:
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Heparin level reported in IU/mL.
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Logistics
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Test Indications:
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Measurement of unfractionated heparin levels in patients treated for thrombotic disease. Recommended for use in place of the APTT at Children’s Hospitals and Clinics.
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Lab Testing Sections:
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Coagulation
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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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2 hours
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Special Instructions:
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Do Not draw through a heparinzed line.
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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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1.8 mL or 2.7 mL blood
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Processed Volume:
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0.9 mL (Minimum: 0.5 mL) plasma
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Collection:
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● A clean venipuncture is essential.
● Patient’s with a hematocrit level >55% must have a special tube made to adjust for the hematocrit; contact laboratory for special tube.
● Deliver immediately to the laboratory. Room temperature; Do Not refrigerate.
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Special Processing:
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N/A
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Patient Preparation:
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None
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Sample Rejection:
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Improper tube; clotted specimens; underfilled tubes; hemolyzed specimens; mislabeled or unlabeled specimens
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Interpretive
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Reference Range:
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Normal: <0.01 IU/mL (patient not on heparin)
Therapeutic Range: 0.3 to 0.7 IU/mL
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Critical Values:
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>1.00 IU/mL
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Limitations:
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The test cannot distinguish between unfractionated and low molecular weight heparin. The correct assay must be requested for the type of heparin the patient is receiving or the results will be off by a factor of 2 to 3. The plasma cannot be treated for heparin removal.
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Methodology:
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Chromogenic Anti-Xa
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References:
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Rosborough TK (1997) Comparison of Anti-Factor Xa Heparin Activity and Activated Partial Thromboplastin Time in 2773 Plasma Samples from Unfractionated Heparin-Treated Patients, AJCP 108:6, 662-668
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Bick RL (1996) Heparin Therapy and Monitoring Guildelines and Practice Parameters for Clinical and Laboratory Approaches, Clin Appl Thrombosis Hemostasis, 2 (Suppl) 512-520
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