Name: Antithrombin III, Activity
Test Name: Antithrombin III, Activity
Health Link Test Code: XAT3
LIS Test Code: A3AC
CPT Code(s): 85300
Methodology: Chromogenic Anti-Xa Assay
Antithrombin is a protein that inhibits thrombin, activated factor X (Xa) and other serine protease enzymes. This test is usually part of a hypercoagulation workup. Test may be falsely low when patient is on heparin.
Days Performed: Mon-Fri, dayshift - day varies. Specimens are accepted at any time. Testing required during off hours must be approved by a Coagulation physician. Call 263-5005 before collection.
In-Lab Turnaround Time: 4 - 7 days.
Stat In-Lab Turnaround Time: 1 day.
Collection Container: Light blue top (3.2% NaCitrate)
Do NOT draw through a line containing heparin. The venipuncture MUST be atraumatic to avoid hemolysis and contamination with tissue factors and platelets. Tube must be allowed to fill completely. Indicate if patient is receiving anticoagulant (warfarin/Heparin/Vitamin K antagonist), direct thrombin inhibitor or fibrinolytic agent therapy and duration.
If unable to collect 1.8 ml tube (pediatrics only) please call UWHC Coagulation Lab at (608) 263-9617 or UWHC Special Coagulation Lab at (608) 263-5005 for alternate tube and instructions.
Collection Volume: Full 3.5 mL tube
Pediatric Collection Volume: Pediatric tube filled to fill mark
4 hours on a spun tube
2 weeks at -20°C; 6 months at -70°C
Sample Analyzed: Plasma
Testing Volume: 1 mL
Pediatric Testing Volume: 0.5 mL
Centrifuge specimen to yield platelet poor plasma (platelet count should be less than 10 K/µL). Separate plasma and transfer to plastic tube or vial. Freeze plasma within 4 hours of collection at -20°C or below.
Outreach Specimen Processing:
Centrifuge specimen to yield platelet poor plasma (platelet count should be 10 K/µL or less). Separate plasma and transfer to labeled plastic tube and spin again. Transfer plasma from second spin to clean plastic labeled tube or vial. Indicate on tube "spun twice". Freeze plasma within 4 hours of collection at -20°C or below.
Transport whole blood specimen at room temperature to UWHC Hospital Laboratory within 4 hours of collection. See Specimen Processing for instructions if transport criteria are not met. Transport frozen plasma aliquot on dry ice to UWHC Hospital Laboratory.
Hemolyzed specimens, clotted specimens, partially filled tubes and whole blood specimens greater than 4 hours old when received by the laboratory are not acceptable.
|6 months and up:||85-128% NPP|
Antithrombin levels in full-term infants may have decreased levels (>35-40%), which reach adult levels by 90 days postnatal. Healthy, premature infants (30-36 weeks gestation) may have decreased levels which reach adult levels by 180 days postnatal.
Interpretation Type: Reference Interval