Test Catalog

Test Id : ATTI

Antithrombin Antigen, Plasma

Useful For
Suggests clinical disorders or settings where the test may be helpful

Assessing abnormal results of the antithrombin activity assay (ATTF / Antithrombin Activity, Plasma), which is recommended as the primary (screening) antithrombin assay


Diagnosing antithrombin deficiency, acquired or congenital, in conjunction with measurement of antithrombin activity


An adjunct in the diagnosis and management of carbohydrate-deficient glycoprotein syndromes

Special Instructions
Library of PDFs including pertinent information and forms related to the test

Method Name
A short description of the method used to perform the test

Latex Immunoassay (LIA)

NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.


Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test

Antithrombin Antigen, P

Lists additional common names for a test, as an aid in searching

Antithrombin III, Immunologic, Plasma

AT III Antigen/Immunologic

AT3 Antigen/Immunologic

Specimen Type
Describes the specimen type validated for testing

Plasma Na Cit

Ordering Guidance

Antithrombin activity (ATTF / Antithrombin Activity, Plasma) is usually used for monitoring treatment of antithrombin deficiency disorders, including infusion of antithrombin therapeutic concentrate.

Necessary Information

If patient is being treated with heparin, this should be noted as heparin treatment may lower plasma antithrombin.

Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing

Patient Preparation: Fasting preferred

Collection Container/Tube: Light-blue top (citrate)

Submission Container/Tube: Polypropylene vial

Specimen Volume: 1 mL

Collection Instructions:

1. For complete instructions, see Coagulation Guidelines for Specimen Handling and Processing.

2. Centrifuge, transfer all plasma into a plastic vial, and centrifuge plasma again.

3. Aliquot plasma into a plastic vial leaving 0.25 mL in the bottom of centrifuged vial.

4. Freeze plasma immediately (no longer than 4 hours after collection) at -20 degrees C or, ideally, < or =-40 degrees C.

Additional Information:

1. Double-centrifuged specimen is critical for accurate results as platelet contamination may cause spurious results.

2. Each coagulation assay requested should have its own vial.

Special Instructions
Library of PDFs including pertinent information and forms related to the test


Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the testing laboratory. The minimum volume is sufficient for one attempt at testing.

0.5 mL

Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected

Gross hemolysis Reject
Gross lipemia Reject
Gross icterus Reject

Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included

Specimen Type Temperature Time Special Container
Plasma Na Cit Frozen 14 days

Useful For
Suggests clinical disorders or settings where the test may be helpful

Assessing abnormal results of the antithrombin activity assay (ATTF / Antithrombin Activity, Plasma), which is recommended as the primary (screening) antithrombin assay


Diagnosing antithrombin deficiency, acquired or congenital, in conjunction with measurement of antithrombin activity


An adjunct in the diagnosis and management of carbohydrate-deficient glycoprotein syndromes

Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Antithrombin is a member of the serine protease inhibitor (serpin) superfamily. It is the principal plasma anticoagulant serpin mediating inactivation of serine protease procoagulant enzymes, chiefly thrombin and coagulation factors Xa and IXa.(1) Heparin and certain other naturally occurring glycosaminoglycans markedly enhance antithrombin's anticoagulant activity (approximately 1000-fold) by providing a template to catalyze formation of covalently bonded, inactive complexes of serine protease and antithrombin that are subsequently cleared from circulation. Antithrombin is the mediator of heparin's anticoagulant activity.


The antithrombin gene on chromosome 1 encodes a glycoprotein of approximately 58,000 molecular weight that is synthesized in the liver and is present in a relatively high plasma concentration (approximately 2.3 mcmol/L). The biological half-life of antithrombin is 2 to 3 days.


Hereditary antithrombin deficiency, a relatively rare, autosomal dominant disorder, produces a thrombotic diathesis (thrombophilia). Individuals with hereditary antithrombin deficiency are usually heterozygous with plasma antithrombin activity results of approximately 40% to 70%. These patients primarily manifest with venous thromboembolism (deep vein thrombosis and pulmonary embolism), with the potential of development as early as adolescence or younger adulthood. More than 100 different variants have been identified throughout the gene, producing either the more common type I defects (low antithrombin activity and antigen) or the rarer type II defects (dysfunctional protein with low activity and normal antigen).(2) Homozygous antithrombin deficiency appears to be incompatible with life.


The incidence of hereditary antithrombin deficiency is approximately 1:2000 to 1:3000 in general populations, although minor deficiency (antithrombin activity =70% to 75%) may be more frequent (approximately 1:350 to 1:650). In populations with venous thrombophilia, approximately 1% to 2% have antithrombin deficiency. Among the recognized hereditary thrombophilic disorders (including deficiencies of proteins C and S, as well as activated protein C-resistance [factor V Leiden variant]), antithrombin deficiency may have the highest phenotypic penetrance (greater risk of venous thromboembolism). Arterial thrombosis (eg, stroke, myocardial infarction) has occasionally been reported in association with hereditary antithrombin deficiency.


Hereditary deficiency of antithrombin activity can also occur because of defective glycosylation of this protein in individuals with carbohydrate-deficient glycoprotein syndromes (CDGS).(3) Antithrombin activity assessment may be useful as an adjunct in the diagnosis and management of CDGS.


Acquired deficiency of antithrombin is much more common than hereditary deficiency. Acquired deficiency can occur due to:

-Heparin therapy (catalysis of antithrombin consumption)

-Intravascular coagulation and fibrinolysis (ICF) or disseminated intravascular coagulation (DIC), and other consumptive coagulopathies

-Liver disease (decreased synthesis and/or increased consumption)

-Nephrotic syndrome (urinary protein loss)

-L-asparaginase chemotherapy (decreased synthesis)

-Other conditions(1)


In general, the clinical implications (thrombotic risk) of antithrombin deficiency in these disorders are not well defined, although antithrombin replacement in severe DIC/IFC is being evaluated.(4) Assay of antithrombin activity may be of diagnostic or prognostic value in some acquired deficiency states.

Reference Values
Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

Adults: 80-120%

Normal, full-term newborn infants may have decreased levels (> or =35-40%), which reach adult levels by 180 days postnatal.*

Healthy, premature infants (30-36 weeks gestation) may have decreased levels, which reach adult levels by 180 days postnatal.*

*See Pediatric Hemostasis References section in Coagulation Guidelines for Specimen Handling and Processing.

Provides information to assist in interpretation of the test results

Hereditary antithrombin deficiency is much less common than acquired deficiency. Diagnosis of hereditary deficiency requires clinical correlation, testing of both antithrombin activity and antithrombin antigen, and may be aided by repeated testing and by family studies. DNA-based diagnostic testing may be helpful, but is generally not readily available.


Acquired antithrombin deficiency may occur in association with a number of conditions (see Clinical Information). The clinical significance (thrombotic risk) of acquired antithrombin deficiency is not well established, but accumulating information suggests possible benefit of antithrombin replacement therapy in carefully selected situations.(4)


Increased antithrombin activity has no definite clinical significance.

Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Antithrombin antigen results are potentially affected by:

-Heparin (unfractionated or low-molecular-weight) >4 U/mL

-Hemoglobin >7 g/L

-Bilirubin >500 mg/L

-Lipemia; may lead to an over-estimation of the antithrombin antigen level

-Rheumatoid factor (RF) >800 IU/mL; may lead to overestimation of the antithrombin antigen level

-Anti-rabbit antibodies in certain subjects leads to aberrant results

-Heparin therapy may temporarily decrease plasma antithrombin antigen into the abnormal range

Clinical Reference
Recommendations for in-depth reading of a clinical nature

1. Bock SC: Antithrombin III and heparin cofactor II. In: Colman RW, Hirsh J, Marder VJ, et al, eds. Hemostasis and Thrombosis. 4th ed. Lippencott Williams and Wilkins; 2001:321-333

2. Viazzer H: Hereditary and acquired antithrombin deficiency. Semin Thromb Hemost. 1999;25(3):257-263

3. Conrad J: Antithrombin activity and antigen. In: Laboratory Techniques in Thrombosis-A Manual. 2nd ed. Kluwer Academic Publishers; 1999:121-128

4. Lane DA, Bayston T, Olds RJ, et al: Antithrombin mutation database: 2nd (1997) update. For the Plasma Coagulation Inhibitors Subcommittee of the Scientific and Standardization Committee of the International Society on Thrombosis and Haemostasis. Thromb Haemost. 1997 Jan;77(1):197-211

5. Van Cott EM, Orlando C, Moore GW, et al: Recommendations for clinical laboratory testing for antithrombin deficiency; Communication from the SSC of the ISTH. J Thromb Haemost. 2020 Jan;18(1):17-22

Special Instructions
Library of PDFs including pertinent information and forms related to the test

Method Description
Describes how the test is performed and provides a method-specific reference

This assay is performed on the Instrumentation Laboratory ACL TOP using the Diagnostica Stago LIATEST AT III kit. Antithrombin antigen is determined using automated latex immunoassay (LIA) methodology. Patient plasma, containing antithrombin antigen, is combined with a latex reagent containing rabbit antihuman antibodies. An antigen-antibody reaction takes place, causing the latex particles to agglutinate and form aggregates. The aggregates form diameters greater than the wavelength of the light (405 nm) passing through causing absorption of the light. This change in absorption is measured over time and reported as delta optical density. The increase in absorption is proportional to the concentration of antithrombin antigen present in the sample.(Package insert: LIATEST AT III. Diagnostica Stago S.A.S.; Rev. 02/2015)

PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information


Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.

Monday through Friday

Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.

Same day/1 to 4 days

Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded

7 days

Performing Laboratory Location
Indicates the location of the laboratory that performs the test


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Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.

This test has been modified from the manufacturer's instructions. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.

CPT codes are provided by the performing laboratory.


LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.

Test Id Test Order Name Order LOINC Value
ATTI Antithrombin Antigen, P 27812-7
Result Id Test Result Name Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
ATTI Antithrombin Antigen, P 27812-7

Test Setup Resources

Setup Files
Test setup information contains test file definition details to support order and result interfacing between Mayo Clinic Laboratories and your Laboratory Information System.

Excel | Pdf

Sample Reports
Normal and Abnormal sample reports are provided as references for report appearance.

Normal Reports | Abnormal Reports

SI Sample Reports
International System (SI) of Unit reports are provided for a limited number of tests. These reports are intended for international account use and are only available through MayoLINK accounts that have been defined to receive them.

SI Normal Reports | SI Abnormal Reports