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Order Code AATTF Antithrombin Activity, with Reflex to Antithrombin Antigen, Plasma


Ordering Guidance


Coagulation testing is highly complex, often requiring the performance of multiple assays and correlation with clinical information. For that reason, consider ordering AATHR / Thrombophilia Profile, Plasma and Whole Blood.



Specimen Required


Specimen Type: Platelet-poor plasma

Collection Container/Tube: Light-blue top (3.2% sodium citrate)

Submission Container/Tube: Plastic 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° C or ideally, at or below -40° C.

Additional Information:

1. A 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.

3. Heparin treatment may lower plasma antithrombin.


Useful For

Diagnosis of antithrombin deficiency, acquired or congenital

Testing Algorithm

If the activity is abnormal low, then the summary interpretation and antigen will be performed at an additional charge.

Method Name

Chromogenic Assay

Reporting Name

Antithrombin Activity, w/ Reflex, P

Specimen Type

Plasma Na Cit

Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time
Plasma Na Cit Frozen 14 days

Reject Due To

Gross hemolysis Reject
Gross lipemia Reject
Gross icterus Reject

Reference Values

Normal values:

80%-130%

 

Normal, full-term newborn infants have lower levels (≥35%-40%) that reach normal values by 90 days of age. Premature infants (30-36 weeks gestation) have lower levels that reach normal values by 180 days of age.

Method Description

Patient plasma, containing antithrombin, is mixed and incubated with reagent containing factor Xa and excess heparin. Factor Xa activity in the reagent is rapidly inhibited by antithrombin. Residual factor Xa activity is then measured using an amidolytic activity assay. This occurs when residual factor Xa lyses chromogenic substrate N-alpha-benzyloxycarbonyl-D-arginyl-L-glycyl-L-arginine-p-nitroaniline-dihydrochloride and subsequently releases p-nitroaniline (detected at 405 nm) in a level that is inversely proportional to the amount of antithrombin in the sample. This method is based on inhibition of factor Xa and, therefore, only higher amounts of heparin cofactor II, alpha-2-macroglobulin, or alpha-1-antitrypsin will influence the assay.(Package insert: HemosIL Liquid Antithrombin. Instrumentation Laboratory Comp; 06/2017)

Day(s) Performed

Monday through Saturday

Performing Laboratory

Mayo Clinic Laboratories in Rochester

CPT Code Information

85300 - AATTF

85301 – ATTI (if appropriate)

Reflex Tests

Test ID Reporting Name Available Separately Always Performed
AATTA Antithrombin Summary Interp No No
ATTI Antithrombin Antigen, P Yes No

Forms

If not ordering electronically, complete, print, and send a Coagulation Test Request (T753) with the specimen.