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Test Code AT3ACB or LAB311 Antithrombin 3 Activity, Plasma

Important Note

Please contact the laboratory if the patient's hematocrit is over 55%, as a special tube must be provided for the blood draw.

Profile Information

Test ID  

Reporting Name

Available Separately

Always Performed

AT3ACT

Antithrombin Activity

No

Yes

RAGIII

Antithrombin Antigen*

Yes

No

*Reflex test, only performed when Antithrombin III is below the normal range.

Specimen Requirements

Specimen Type:

Whole Blood

Container Type:

Blue top: 2.7 mL or 1.8 mL 

Optimal Collection Volume:
  • 2.7 mL in solid blue top tube or 1.8 mL in clear blue top tube.  The correct fill volume is indicated by the etched line on the tube.
  • Click here to view the specimen collection guide for blue top (citrate) tubes.

Collection Instructions:
  1. Gently invert tube 5-10 times to mix blood.
  2. If collected through a blood collection set (butterfly), a discard tube must first be drawn to eliminate dead space from the tubing.

Specimen Transport Temperature:

 
  • Room temperature for up to 4 hours. If testing is delayed, separate plasma and freeze (see outpatient collection instructions below).
  • Specimens cannot be refrigerated

Processing Instructions:
  1. Centrifuge sample within 4 hours of collection. Platelet-poor plasma must be obtained per laboratory procedure.
  2. If testing will be delayed >4 hours from collection, aliquot plasma into a separate vial and freeze immediately.

Outpatient collections

  1. Spin down the sample, remove plasma, and spin plasma again to obtain platelet-poor plasma.
  2. Separate the platelet-poor plasma into a screw-top vial.
  3. Freeze plasma immediately.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Specimen Stability

Specimen Type

Temperature

Time

Whole Blood

Ambient

4 hours

Platelet poor plasma

Ambient 

4 hours

Platelet poor plasma

Frozen at -20 C

18 months

Specimen Rejection Criteria

  • Tube underfilled
  • Clotted specimen
  • sample not processed and frozen within 4 hours of collection

Useful For

  • Diagnosis of antithrombin deficiency, acquired or congenital.
  • Monitoring treatment of antithrombin deficiency disorders, including infusion of antithrombin therapeutic concentrate.
  • Because coagulation testing and its interpretation are complex, Bronson Laboratory suggests ordering the Thrombophilia Cascade (LAB2692).

Methodology

Performed using the Hemosil Antithrombin kit on the ACL TOP 500.

Reference Ranges

80-130%

  • Values less than 80% reflex the Antithrombin Antigen assay, which is performed at Mayo Laboratories.

Day(s) Performed

Monday, Wednesday, and Friday, day shift only.

Expected TAT

1-3 days

Performing Laboratory

Bronson Laboratory, Coagulation - Kalamazoo

Sample Retention Time

1 month

CPT Code

  • Antithrombin III Activity - 85300
  • Reflex Antithrombin III Antigen - 85301*

*Billed when Antithrombin III Activity is less than 80%

LOINC Code

27811-9