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Antithrombin (Functional) (LAB002080)
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:



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


If the testing is not completed within 4 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:
  • Clotted and hemolyzed plasma samples are unacceptable and must be redrawn.
  • Wrong tube or anticoagulant.
  • Wrong anticoagulant ratio (over or underfilled tubes).
  • Not centrifuged within the acceptable time after collection.
  • Whole blood or plasma refrigerated or placed on ice prior to testing.
  • Unlabeled.
  • Mislabeled.


Reference Range:

83 - 128 %


Infant and child reference ranges have not yet been established at UTMB.

Turnaround Time:


The hours of operation are Monday – Friday from 8:00 am to 4:00 pm with an expected TAT of 4 hours. STAT requests after business hours will be evaluated and handled by the on-call staff member.




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


CLS Specialty Lab

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Clinical Indication:

Measures functional AT and is a potential valuable test for patients having personal/family history of thrombosis or antithrombin deficiency.

CPT 4 Code:




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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