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HEPARIN NEUTRALIZATION Synonyms: Hep Neut, Hepzyme CPT Code(s): 85525 Test Order Mnemonic: Hepneut Applies To: Rule out heparin contamination as the reason for abnormal coagulation results on PT and aPTT. Test Includes: Patient results with the comment: “Heparin neutralization performed” Request Form: Hematology A Collection: Routine venipuncture. Discard 1st ml of blood or collect other tubes (EDTA, Serum-separator, etc.) prior to collecting sample in citrate (light blue-top tube). Storage Instructions: Viable for 4 hours at room temperature. If time from draw to delivery is to be greater than 4 hours, centrifuge the sample, separate the plasma from cells, and snap freeze (-70°C) the plasma. Snap frozen plasma is viable indefinitely. Causes for Rejection: 3 .8% sodium citrate tubes, QNS, clotted, severely hemolyzed, greater than 4 hours old, identification error, processed and/or stored improperly. Availability: Accepted 24 hours/day at Sample Management, Room 5.136 McCullough. Turnaround Time: STAT: 1 hour; Routine: 4 hours Special Instructions: Deliver sample to lab within ½ hour for best results. Accepted up to 4 hours at room temperature. Specimen: Blood Volume: 4.5 ml Minimum Volume: Call lab Container: 3.2% Sodium citrate tube (light blue-top) [NOTE: 3.8% sodium citrate tubes will NOT be accepted.] Reference Range: Differences in test values before and after plasma treatment with Hepzyme indicates the presence of heparin in the sample. Hepzyme will neutralize heparin that may have contaminated the sample, and . in-vivo heparin from patients on heparin therapy. Therefore, a heparin neutralization should not be done on patient’s whose heparin therapy is being monitored with the aPTT. See “Collection and Handling of Coagulation Specimens” for instructions on how to avoid heparin contamination. Test Methodology: Platelet poor plasma is added to a vial of Hepzyme (Heparinase is specific for heparin, and cleaves the heparin molecule producing oligosaccharides that have lost their thrombotic activity), and allowed to sit at room temp for 15 minutes. The plasma is then tested for PT and/or aPTT. Hepzyme can neutralize up to 2 USP units of unfractionated heparin in 1 ml of citrated plasma. If heparin level in plasma is greater than 2 USP units, but less than 4 USP units, sequential neutralization may be performed. Limitations: In evaluating Hepzyme results of patients during heparin therapy, the presence of TFPI (Tissue Factor Pathway Inhibitor) should be considered. The levels of TFPI increase several fold following heparin injection. An increase in TFPI activity has been associated with an anticoagulant effect that is not removed by heparin neutralization and may result in prolonged clotting times. For patients receiving oral anticoagulants, thrombolytic therapy, or patients with circulating inhibitors or anti-phospholipid antibodies, the medication and clinical histories should be considered when interpreting results. These patients may have underlying conditions that result in prolongation of the APTT and/or PT in the absence of heparin. Thrombin Times should not be performed on samples that have been sequentially neutralized. Revised 12/10/07 by W.Russo, MT(ASCP) |
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