ANTITHROMBIN (AT-III)

Message

Coagulation

Test Code

LAB311

Alias/See Also

Antithrombin

CPT Codes
85300

Preferred Specimen

Blue top tube 3.2% citrated tube, plasma TUBE MUST BE FULL

Minimum Volume

Full Blue top tube

Instructions

Specimen to be delivered to Coagulation department STAT. Notify CLS upon arrival. **Testing must be completed within 4 hours of collection.

LAB: If testing is not to be done within 2 hours, centrifuge light blue-top for 2 minutes at 7200 rpm (STAT coag. centrifuge) within 60 minutes of collection. Using a plastic pipette, remove plasma, taking care to avoid the WBC/platelet buffy layer and place into a plastic vial.
Centrifuge aliquoted plasma a second time and transfer platelet-poor plasma into a new plastic vial and place in 2-8℃ refrigerator or freeze -20℃ if delay longer than 1 hour.

Freeze aliquot at -20oC for at least 1 hour when sending to alternate campus for testing.

Transport Temperature

Ambient: whole blood (stable 1 hour)
Frozen: plasma frozen for at least 1-2 hours

Specimen Stability

Processed Platelet Poor Plasma:
Room Temp – 4 hours
Refrigerated 2-8° C – 4 hours
Frozen (-20° C) – 1 Month
Frozen (-70° C) – 6 Months
Sample may be frozen and maintained at -70oC for two freeze/thaw cycle

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

Underfilled tubes
Specimen transported on ice

Methodology
The Antithrombin level in patient plasma is measured in two stages: Incubation of the plasma with the Factor Xa reagent in the presence of an excess of heparin. Quantification of the residual FXa activity with a synthetic chromogenic substrate. The paranitroaniline released is monitored kinetically at 405 nm and is inversely proportional to the Antithrombin level in the test sample.

FDA Status
Cleared

Report Available

STAT: 1 hour
Routine: Same Day

Limitations

Hemoglobin up to 500 mg/dL; Bilirubin up to 40 mg/dL; Triglyceride up to 2300 mg/dL; Heparin (UF or LMW) Up to 4 U/ml; Alpha1-antitrypsin up to 4 mg/mL; Alpha2-macroglobulin up to 7 mg/mL.

Reference Range

83 - 128%

Clinical Significance

Antithrombin is the major inhibitor of blood coagulation and is essential for effective Heparin Therapy.

Performing Laboratory
HHN

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.