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Antithrombin III Activity, reflex to Antigen

Test Name
Antithrombin III Activity, reflex to Antigen
Alternate Names
antithrombin iii
antithrombin iii functional
at iii
at iii activity
at iii functional
Test Code
Specimen Requirements
2 aliquots, each with a minimum of 1.0 mL frozen plasma
Supplies for Submission
Light Blue Top
Specimen Collection
  1. Fill up a Light Blue Top tube as completely as possible and mix by gently inverting the tube 5-6 times.
    Inadequate filling will distort the exact ratio of 1 part sodium citrate to 9 parts blood required for accurate results.
  2. Immediately centrifuge the specimen at 1500 RCF for 15 minutes.
  3. Pipette the supernatant plasma and transfer to a plastic transport tube.
  4. Re-centrifuge plasma in the transport tube at 1500 RCF for 15 minutes to make sure that no red blood cells are present.
  5. Pipette the top two-thirds of the supernatant plasma and transfer 2.0 mL to a second transport tube, labeled with two patient identifiers.
  6. Also, label this aliquot tube as citrate plasma and immediately freeze at -20 °C or lower for transport.
Storage Requirements
Critical Frozen (CFZ).
After separation from cells, specimens are stable if frozen for 1 month (- 20 °C).
Causes for Rejections
Specimens with the following conditions are not accepted:
  • hemolysis
  • clotted
  • refrigerated
  • submitted in inappropriate anticoagulant
CPT Code
85300, add 85301 if reflex