Antithrombin III, Functional

Test Code

ATHR3

Alias/See Also

ATIII, Thrombin III

CPT Codes
85300

Preferred Specimen

Citrate (BLU)

Instructions

Collect whole blood in 3.2% buffered sodium citrate (9:1 blood to sodium citrate). Venipuncture must be atraumatic.

Specimen Stability

Centrifuge at 4,500 RPM (high) for 10 minutes. Plasma platelet count should be less than 10,000. Test within 4 hours of collection.
If testing is to be delayed more than four hours after collection, immediately separate plasma into a clean, polystyrene tube, cap and store below -20°C up to two weeks or -70°C up to 6 months.
In patients with hematocrit values greater than 55%, the citrate concentration must be adjusted so that a proper plasma/anticoagulant volume is maintained.

Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)

Reject hemolyzed, clotted, overfilled tubes or short draw (<90%) samples.

Reference Range

1 day to 6 years of age: 39-108%
6 years and older: 80-120%

Performing Laboratory
CRMC Laboratory

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.