Antithrombin III Antigen, Immunologic (ATTI)

Marshfield Lab Public WebSite

Marshfield Clinic Public WebSite

Test Code: MISC

Overview
Ordering
Specimen
Performing
Clinical/Interpretive
Contacts
Coding

Synonyms/Keywords

Antithrombin III, Immunologic, Plasma; AT III Antigen/Immunologic,; AT3 Antigen/Immunologic

Useful For

Assessing abnormal results of the antithrombin activity assay. (ATTF/9030 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

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

Specimen Requirements

Specimen Type	Preferred Container/Tube	Acceptable Container/Tube	Specimen Volume	Specimen Minimum Volume (allows for 1 repeat)	Pediatric Minimum Volume (no repeat)
Plasma	Citrated Blue Top Tube (BTT)		1 mL	0.5 mL

Collection Processing Instructions

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

Submit sample (platelet poor plasma) in a plastic vial.

Collection Instructions:

1. Centrifuge, remove plasma, and centrifuge plasma again.

2. 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.

Specimen Stability Information

Specimen Type	Temperature	Time
Plasma	Frozen	14 days

Rejection Criteria

Gross hemolysis
Gross lipemia
Gross icterus

Interference

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

Performing Laboratory Information

Performing Location	Day(s) Test Performed	Report Available	Methodology/Instrumentation
Mayo Clinic Laboratories	Monday through Friday	1 to 4 days	Latex Immunoassay (LIA)

Reference Lab

Mayo Clinic Laboratories

Reference Range Information

Adults: 80-130%

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.*

Interpretation

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.

Outreach CPTs

CPT	Modifier (if needed)	Quantity	Description	Comments
85301