Laboratory Test Directory

ANTITHROMBIN III (Functional): (089-0443)

Clinical Indication:

Measures functional ATIII and is a valuable test for patients having personal/family history of thrombosis.

Test Mnemonic:

 AT3

Methodology:

 Chromogenic

Performed:

 Accepted 24 hours/day at Sample Management, Room 5.136 McCullough.

Turnaround Time:

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

Specimen Requirements:

Collect: 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.

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

Storage/Transport: NOTE: 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.

Stability:  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 (3.8% sodium citrate), high hematocrit (> 55%), sample identification error, sample processed/transported, and/or stored improperly.

Clinical Information:

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

Reference Range:

89 - 130 %

CPT 4 Code:

 85300

Reviewed: 3/20/13

W. Russo, MT(ASCP)

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-9 code or its verbal equivalent.