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ANTITHROMBIN (Functional) (089-0443)
Test Mnemonic:


Specimen Requirements:

 Blue-topped (3.2% sodium-citrate) tube. 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


If delivery time is to be greater than 4 hours from time of draw, centrifuge the specimen for 15 minutes at 2000-2500g.

·         Transfer plasma to 12x75 plastic tube

·         Cap tube and re-spin  for 15 minutes at 2000-2500g

·         CAREFULLY remove from centrifuge without disturbing any platelets and/or cell pellets that might be on the bottom or sides of the tube.

·         Carefully transfer plasma into freezer tubes (plastic screw-top cryo-tubes) for testing or freezing.

Specimen Preparation:

Samples should be received in laboratory within ½ hour of draw for best results.  


Whole blood 4 hours at room temperature. Plasma 8 hours at 20+/- 5°C.  Frozen at -20 °C 1 month. 

Causes for Rejection:

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

Reference Range:

89 - 130 %

Turnaround Time:

Test performed once per week; maximum 7 day turnaround time.




Accepted 24 hours/day at Sample Management, Room 7.412 CSW.



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:



Heparin > 1IU/mL, oral contraceptives, Elevated levels of hemoglobin, bilirubin or lipids, Estrogen, steroids.

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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