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Test Code LAB311 Antithrombin III

Clinical Information

AT3 levels are used as a possible indicator of hypercoagulability, and to test for the hereditary deficiency of antithrombin. AT3 levels might also be of use in cases of suspected heparin failure especially prior to heparinization.

Synonym

  • AT
  • Antithrombin Activity
  • Antithrombin Functional
  • ATIII
  • AT3

Specimen Required

Preferred Container/Tube: 3.2% Citrate Blue Top - 2.7 mL
Specimen Volume: 2.7 mL
Acceptable Container/Tube: 3.2% Citrate Blue Top - 1.8 mL
Specimen Volume: 1.8 mL
Platelet poor plasma (PPP):
Specimen Volume: 2 - 1 mL aliquots platelet poor plasma (PPP)
Specimen Minimum Volume: 1 - 1 mL aliquot platelet poor plasma (PPP)

Specimen Collection Information

Samples from outreach locations must be received as frozen plasma.  

For sending frozen specimens, process specimens immediately upon collection. Centrifuge capped specimen tube at a speed and time required to consistently produce platelet-poor plasma (platelet count <10 K/uL). Check cells for clot. Do not send for testing if the sample is clotted. Transfer plasma into 2 plastic aliquot tubes and freeze. DO NOT transport until specimens are completely frozen. 

Note: All specimens transported as frozen plasma must remain frozen in transit. 

Specimen Stability Information

Ambient: 
     Whole blood: 1 hours
     Platelet poor plasma: 2 hours
Frozen: 
      Platelet poor plasma: PPP removed from the cells and frozen at -20°C or ideally -70°C.

Rejected Due To

  • Ambient specimens >4 hours old
  • Clotted specimens
  • Underfilled or overfilled tube

Reference Values

0-4 days: 39-87 %
5-29 days: 41-93 %
30-89 days: 48-108 %
90-179 days: 73-121 %
180-365 days: 84-124 %
1-5 years: 82-139 %
6-10 years: 90-131 %
11-16 years: 77-132 %
17+ years: 85-118 %

Cautions

Test is not indicated for patients on heparin, low-molecular-weight heparin, or direct thrombin inhibitor therapy. This test is not indicated for inpatient evaluation of acute thrombosis.

Method Description

Chromogenic measurement at 405nm

Performing Lab

Clinical Lab UH

Day(s) Performed

Monday through Friday (excludes OSU holidays)

Reporting Name

Antithrombin Activity

CPT Code Information

85300

LOINC Code Information

27811-9

Report Available

Same day/1 day