Antithrombin (AT) Antigen (Immunologic)

TEST: 015057
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CPT: 85301
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Special Instructions

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.

Expected Turnaround Time

2 - 3 days

Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.

Related Information

Related Documents

For more information, please view the literature below.

Procedures for Hemostasis and Thrombosis: A Clinical Test Compendium

Specimen Requirements

Specimen

Plasma, frozen

Volume

2 mL

Minimum Volume

1 mL (Note: This volume does not allow for repeat testing.)

Container

Blue-top (sodium citrate) tube

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.

Please print and use the Volume Guide for Coagulation Testing to ensure proper draw volume.

Storage Instructions

Freeze.

Stability Requirements

Temperature

Period

Frozen

28 days

Freeze/thaw cycles

Stable x3

Patient Preparation

Do not draw from an arm with a heparin lock or heparinized catheter.

Causes for Rejection

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

Test Details

Use

This test is used for confirmation and characterization of congenital AT deficiency.

Limitations

AT testing should not be performed on patients on heparin therapy because heparin decreases plasma AT levels.6,7 AT results for individuals on warfarin therapy should be interpreted with caution because warfarin can increase levels of AT of patients with heterozygous deficiency into the normal range.7

This test was developed and its performance characteristics determined by Labcorp. It has not been cleared or approved by the Food and Drug Administration.

Methodology

Automated (LIATEST) enzyme immunoassay (EIA)

Reference Interval

In newborns, AT levels are lower than in adults (39% to 89%). Levels gradually reach adult ranges by six months of age.6

Additional Information

See Antithrombin (AT) Deficiency Profile [015594] for more clinical information.

Footnotes

1. Adcock DM, Kressin DC, Marlar RA. Effect of 3.2% vs 3.8% sodium citrate concentration on routine coagulation testing. Am J Clin Pathol. 1997 Jan; 107(1):105-110. 8980376
2. Reneke J, Etzell J, Leslie S, Ng VL, Gottfried EL. Prolonged prothrombin time and activated partial thromboplastin time due to underfilled specimen tubes with 109 mmol/L (3.2%) citrate anticoagulant. Am J Clin Pathol. 1998 Jun; 109(6):754-757. 9620035
3. National Committee for Clinical Laboratory Standardization. Collection, Transport, and Processing of Blood Specimens for Coagulation Testing and General Performance of Coagulation Assays; Approved Guideline. 5th ed. Villanova, Pa: NCCLS; 2008. Document H21-A5:28(5).
4. Gottfried EL, Adachi MM. Prothrombin time and activated partial thromboplastin time can be performed on the first tube. Am J Clin Pathol. 1997 Jun; 107(6):681-683. 9169665
5. McGlasson DL, More L, Best HA, Norris WL, Doe RH, Ray H. Drawing specimens for coagulation testing: Is a second tube necessary? Clin Lab Sci. 1999 May-Jun; 12(3):137-139. 10539100
6. Adcock DM, Gosselin R. Direct oral anticoagulants (DOACs) in the laboratory: 2015 review. Thromb Res. 2015 Jul; 136(1):7-12. 25981138
7. Zwicker J, Bauer KA. Thrombophilia. In: Kitchens CS, Alving BM, Kessler CM eds. Consultative Hemostasis and Thrombosis. Philadelphia, Pa: WB Saunders Co;2002:181-196.

LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
015057 Antithrombin Antigen 27812-7 015057 Antithrombin Antigen % 27812-7

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