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Test Code 62870832 Antithrombin III Activity

Important Note

TML Outreach Instruction: 

Perform expedite processing

Perform platelet-poor processing if specimen will not reach laboratory within timeframe indicated below

Performing Laboratory

Torrance Memorial Laboratories

Specimen Requirements

Specimen Type:  Whole blood

Container/Tube: Blue top (citrate)

Specimen Volume: Tube must be filled

Collection Instructions:

1.  Tube must be filled to the fill line.

2.  If using butterfly, discard tube must be drawn first.

3.  Acceptable:  1.8 mL Citrate Blue top or 2.7 mL Citrate Blue top

Additional Instructions:
1.    Patient should be fasting, if possible
2.    For certain tests, the patient cannot be receiving the following anticoagulant medications:

  • Heparin
  • Warfarin/Coumadin
  • Direct thrombin inhibitor:  Pradaxa (dabigatran), Acova (argatroban)
  • Direct Xa inhibitor:  Xarelto (rivaroxaban), Eliquis (apixaban), Savaysa (edoxaban)
  • tPA (tissue plasmin activator)

Specimen Transport Temperature

Ambient

 

Storage Temp Stability:
Room Temperature: 4 hours, unopened tube with plasma on cells, spun or unspun
Refrigerated:  4 hours, unopened tube with plasma on cells, spun or unspun

Frozen:  2 weeks (frozen plasma at -20 C)

Methodology

Chromogenic

Reference Range

>18 years:  80-130%

 

Interpretive Data

Antithrombin deficiencies due to inherited causes are much less common than those due to acquired causes.

Diagnosis of hereditary deficiency requires clinical correlation, with the prospect of repeat testing (including antithrombin antigen assay), and family studies (with appropriate counseling). DNA-based diagnostic testing may be helpful. 

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.

Antithrombin deficiency, acquired or congenital, may contribute to the phenomenon of "heparin therapy resistance" (requirement of larger heparin doses than expected for achievement of therapeutic anticoagulation responses). However, it may more often have other pathophysiology, such as "acute-phase" elevation of coagulation factor VIII or plasma heparin-binding proteins.


Increased antithrombin activity is of unknown hemostatic significance. Direct factor Xa inhibitors, rivaroxaban (Xarelto), apixaban (Eliquis), and edoxaban (Savaysa) may falsely elevate the antithrombin activity and mask a diagnosis of antithrombin deficiency.


Limitations:
1.  Patient should not be on the following medications as the results may be falsely elevated:
     *    Direct thrombin inhibitor: Pradaxa (dabigatran), Acova (argatroban)
     *    Direct Xa inhibitor: Xarelto (rivaroxaban), Eliquis (apixaban), Savaysa (edoxaban)
     *    tPA (tissue plasma activator)

 

Day(s) Test Set Up/TAT

Performed:

Daily

Available STAT

 

TAT:

STAT < 1 hr

Routine < 4 hrs

Aliases

None

CPT Code

85300