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ANTITHROMBIN (AT-III)
MessageCoagulation
Test Code
LAB311
Alias/See Also
Antithrombin III Activity
Antithrombin
AT-III
Antithrombin
AT-III
CPT Codes
85300
Preferred Specimen
Blue top 3.2% citrated tube, plasma
Note: Do NOT place blue top tube on ice
Note: Do NOT place blue top tube on ice
Minimum Volume
2.7 mL whole blood filled to the designated line on specimen container (blue top tube, citrate)
Other Acceptable Specimens
1.8 mL Low Volume blue top tube, citrated (microtainer)
Instructions
LAB: Centrifuge in validated Platelet Poor Plasma Centrifuge for 2 minutes at 7200 rpm. Specimen to be delivered to Coagulation department STAT. Notify CLS upon arrival.
**Testing must be completed within 4 hours of collection.
Note: If unable to deliver whole blood to testing laboratory within stability time, platelet poor plasma should be aliquoted and placed in freezer. 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. Once thawed, specimen must be tested within 2 hours.
Freeze aliquot at -20℃ for at least 1 hour when sending to alternate campus for testing.
**Testing must be completed within 4 hours of collection.
Note: If unable to deliver whole blood to testing laboratory within stability time, platelet poor plasma should be aliquoted and placed in freezer. 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. Once thawed, specimen must be tested within 2 hours.
Freeze aliquot at -20℃ 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
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
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?)
Hemolyzed, clotted specimen, contaminated, underfilled - QNS, overfilled tube, whole blood 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
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
