Antithrombin (AT) Activity
Also known as: Antithrombin III Activity, Antithrombin III, Functional, AT3 Activity, Factor Xa Inhibitor, Heparin Cofactor Activity
Use
Confirmation and characterization of acquired or congenital AT deficiency
Special Instructions
If the patient's hematocrit exceeds 55%, the volume of citrate in the collection tube must be adjusted. The test should not be performed on patients receiving unfractionated heparin therapy, and results should be interpreted with caution in individuals on warfarin therapy.
Limitations
AT testing should not be performed on patients on unfractionated heparin therapy because heparin decreases plasma AT levels. AT results for individuals on warfarin therapy should be interpreted with caution as warfarin can increase levels of AT, potentially masking deficiencies. Thrombin inhibitors do not interfere with the assay unless it is thrombin-based. Direct Xa inhibitors will interfere with the assay, elevating results and potentially masking deficiencies.
Methodology
Automated Analyzer (Clinical Chemistry)
Biomarkers
LOINC Codes
- 27811-9
- 27811-9
Result Turnaround Time
2-3 days
Related Documents
For more information, please review the documents below
Specimen
Plasma
Volume
1 mL
Minimum Volume
Not provided
Container
Blue-top (sodium citrate) tube
Collection Instructions
Blood should be collected in a blue-top tube containing 3.2% buffered sodium citrate. Ensure proper blood-to-anticoagulant ratio by filling evacuated tubes completely. Mix immediately by gentle inversion at least six times. A discard tube is needed if collected using a winged set. Non-citrate tubes should be collected first if required.
Patient Preparation
Do not draw from an arm with a heparin lock or heparinized catheter.
Storage Instructions
Freeze.
Causes for Rejection
Severe hemolysis; improper labeling; clotted specimen; specimen diluted with IV fluids; samples thawed in transit; improper sample type; sample out of stability
Stability Requirements
| Temperature | Period |
|---|---|
| Frozen | 28 days |