Antithrombin Activity

Test ID: 

706584

CPT code:

85300

Synonyms:

• Antithrombin III Activity
• Antithrombin III, Functional
• AT3 Activity
• Factor Xa Inhibitor
• Heparin Cofactor Activity
• Serine Protease Inhibitor

Clinical Use:

Confirmation and characterization of acquired or congenital AT deficiency

Specimen Type:

Plasma, frozen

Requested Volume: 

2 mL

Minimum Volume: 

1 mL

Container Type: 

Blue-top (sodium citrate) tube

Patient Preparation: 

Do not draw from an arm with a heparin lock or heparinized catheter. Patients ideally should not be on unfractionated heparin or direct Xa inhibitor anticoagulant therapy.

Collection:

Blood should be collected in a blue-top tube containing 3.2% buffered sodium citrate.1 Evacuated collection tubes must be filled to completion to ensure a proper blood-to-anticoagulant ratio.2,3 The sample should be mixed immediately by gentle inversion at least six times to ensure adequate mixing of the anticoagulant with the blood. A discard tube is not required prior to collection of coagulation samples unless the sample is collected using a winged (butterfly) collection system. With a winged blood collection set a discard tube should be drawn first to account for the dead space of the tubing and prevent under-filling of the evacuated tube.4,5 When noncitrate tubes are collected for other tests, collect sterile and nonadditive (red-top) tubes prior to citrate (blue-top) tubes. Any tube containing an alternative anticoagulant should be collected after the blue-top tube. Gel-barrier tubes and serum tubes with clot initiators should also be collected after the citrate tubes.

Storage Instructions:

Freeze.

Rejection Criteria

Severe hemolysis; improper labeling; clotted specimen; specimen diluted with IV fluids; samples thawed in transit; improper sample type; sample out of stability