Veripath Test Directory

Epic Test Name Antithrombin Activity
Synonyms AT Activity
Antithrombin Activity (Functional)
Description Antithrombin (AT) is a natural anti-coagulant that inactivates the serine proteases. As an inhibitor of thrombin, tha tactivity of AT is dramatically enhanced by heparin. It also inhibits Factor Xa and to a lesser extent the Factors IXa, XIa, XIIa, as well as plasmin and kallikrein. Hereditary heterozygous AT deficiency is associated with recurrent thrombosis, mostly venous. Chromogenic assay is utilized to measure functional activity of antithrombin.
Specimen Requirements 
Container 3 mL Light blue (3.2% sodium citrate) collection tube
Specimen Type Blood
Preferred Collection Volume 3 mL
Minimum Collection Volume Adult: 2 mL, Neonates : 2 mL
Collection Instructions When drawing specimens for coagulation testing, always draw a "pilot" tube (7-10ml plain red top tube), completely filled. This removes tissue fluid contamination. Samples should be obtained from peripheral vein wheneever possible. If drawn from indwelling catheter, the line should be flushed with 15mL of saline. After irrigation, a "pilot" tube should be drawn and discarded.
Specimen Handling In-house patients, transport at room temperature.
Out-side client, follow collection instructions and the steps below:
1. Spin light blue top tube. Remove plasma avoiding platelet/buffy coat layer. Spin plasma again to remove top portion of plasma ans place 1mL of PLATELET-POOR PLASMA in plastic tube. (Glass tube unacceptable). Double-centrifugation is critical for accurate results as platelet contamination may cause erroneous results.
2. Plasma must be frozen within 4 hours of collection. CRITICAL WARNING: Specimens must remain frozen until ready to test. Submit separate aliquots when multiple tests are ordered on the same patient specimen.
Rejection Criteria Hemolysis, clotted, short sample, >4 hrs old (if not frozen), thawed plasma, heparin contamination.
Methodology Chromogenic.
Reference Range 84 - 124%
CPT Code(s) 85300
Department Hemostasis/Coagulation
Contact Information Hemostasis Lab; 214-633-4959 Customer Service: 214-633-0400, Toll Free 1-877-887-8136.
Turn Around Time1-5 days
Performed Tuesday & Thursday
Performed by Hemostasis Lab
Notes Patient should be off oral anticoagulants for 2 weeks for accurate measurement. Functional antithrombin values may be decreased in patients on heparin therapy. Patients who are actively thrombosing may have low functional antithrombin values.
Updated/Reviewed 07/23/2016