Antithrombin Activity

If the patient's hematocrit exceeds 55%, the volume of citrate in the collection tube must be adjusted. Refer to Coagulation Collection Procedures for directions.

015040

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

Plasma, FROZEN

1 mL

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 evacutated 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. To avoid delays in turnaround time when requesting multiple tests on frozen samples, please submit separate frozen specimens for each test requested. Print and use the Specimen Collection Bulletin as a tube-filling guide.

Blue-top (sodium citrate) tube

FREEZE

Hemolysis; tubes improperly filled; inadequate labeling, clotted specimens; thawed specimen

Daily 1st and 3rd shift