Antithrombin Activity


Abbrev Code:ANTCH   
Order Code:LAB311Order Name:Antithrombin III
Synonyms:Antithrombin III Functional Assay; Antithrombin III Chromogenic; Anti-thrombin
Methodology:Chromogenic (synthetic substrate) activity assay
CPT Codes: 85300 x1, 85300 x1
Turnaround Time:Within 8 hours if received into the testing laboratory by 2 p.m. Testing performed 6 days per week. With pre-notification, STATs are done within 1 hour after receipt in the testing laboratory.
Associated Links:

Specimen Collection and Processing for Coagulation Specimens



Collection Instructions

Specimen:Blood
Optimal Volume:2.7 mL (in 3 mL tube) - filled to fill line on the tube.
Minimum\Peds Volume:1.8 mL (in 2 mL tube) - filled to fill line on the tube.
Container:Blue Na Citrate, 3.2% - fill to fill line on tube
Collection Instructions:See link to specimen Collection and Processing for Coagulation Specimens.
Causes for Rejection:Underfilled tubes, overfilled tubes, clotted specimens, not received or processed and frozen within 4 hours of collection or, specimen thawed during transit.


Processing and Shipping

Specimen Processing:
  • Process for Platelet Poor Plasma within 4 hours of collection.
  • Aliquot plasma, place clear tape around label, and freeze at -20C or on dry ice within 4 hours of collection.
  • If multiple tests are collected on 1 blue top, split each blue top into 2 aliquots. Minimum 0.5 mL per tube.
  • A maximum of 6 aliquots are needed per collection.

See link to Specimen Collection and Processing for Coagulation Specimens.
Shipping Instructions:
  • Ensure specimen is frozen before shipping.
  • Ship on dry ice, sample must remain frozen during shipping.

See link to Specimen Collection and Processing for Coagulation Specimens.
Test Performed at or Referral Lab UM Special Coag (K)  (UMMC East Bank)


Interpretive

Critical Range:Less than 30%
Reference Range:

Less than 1 d

42-80 %

1-4 d

51-75%

5-29 d

54-80%

30-89 d

63-93%

90-179 d

85-109%

180-364 d

94-114%

1 y and older

85-135%

 

 

Use:Antithrombin inactivates thrombin and other serine proteases (activated Factors 12, 11, 10 and 9). In the absence of heparin, this process is relatively slow. In the presence of heparin, antithrombin almost instantaneously inactivates thrombin. Direct thrombin inhibitors in the sample lead to an over-estimation of the antithrombin level by this method.


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