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Heparin Neutralization (LAB001971, LAB000681)
Test Mnemonic:


Specimen Requirements:

Routine venipuncture; discard 1st mL of blood by collecting a discard tube prior to collecting the blue-topped (3.2% sodium-citrate) tube.  For collections with butterfly blood collection sets, a discard tube should also be collected prior to collection of the blue top to ensure sufficient sample volume. Drawing a discard tube will displace the air from the blood collection set tubing to ensure proper blood draw volume. 


 Blue-topped (3.2% sodium-citrate) tube

Minimum Volume:

1 mL of Plasma

Shipping/Handling instructions:                                                                           
  1. If delivery time is to be greater than 2 hours from time of draw, centrifuge the specimen for 15 minutes at 2000-2500g.
  2. Transfer plasma to 12x75 plastic tube.
  3. Cap tube and re-spin for 15 minutes at 2000-2500g.
  4. Remove from centrifuge without disturbing any platelet and/or cell pellets that might be on the bottom or sides of the tube.
  5. Carefully transfer plasma into freezer tubes (plastic screw-top cryo-tubes) for testing or freezing and be sure to tape the patient's label onto the tube.
  6. Store transport tube in freezer (-20, or -70C) in an upright position.

Specimen Preparation:

Samples should be collected and centrifuged as soon as possible after collection and within 60 minutes.


Fill within +/- 10% from stated capacity. Immediately after draw, gently invert 3-4 times


Ambient - 2 hours; Refrigerated - Unacceptable; Frozen -20oC – 2 weeks, at -70oC - 6 months 

If the testing is not completed within 2 hours, platelet-poor plasma should be removed without disturbing the sedimented cells (buff-coat) and frozen at -20oC or below for short-term storage (up to 2 weeks), or -70oC for 6 months.

Causes for Rejection:

QNS, clotted, severely hemolyzed specimen, specimen greater than 4 hours old, wrong tube, high hematocrit (> 55%), sample identification error, sample processed/transported, and/or stored improperly.

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.

Turnaround Time:

24/7; STAT: 1 hour; ROUTINE: 4 hours


Optical Clot-Based

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 anticoagulant 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.


 Samples are accepted 24 hours per day at Sample Management, 7.412 CSW Bldg.




Clinical Indication:

Rule out heparin contamination as the reason for abnormal coagulation results on PT and aPTT.

CPT 4 Code:



Patient result will have the following comment: “Heparin neutralization 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.

When ordering tests for which Medicare or Medicaid reimbursement will be sought, physicians should only order tests that are medically necessary for the diagnosis or treatment of the patient. Components of the organ or disease panels may be ordered individually. The diagnostic information must substantiate all tests ordered and must be in the form of an ICD-10 code or its verbal equivalent.
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