Antithrombin III Antigen

AT3B

5158

1 mL frozen platelet-poor plasma collected in 3.2% sodium citrate (light blue-top) tube

0.5 mL

Please submit a separate, frozen vial for each special coagulation assay ordered. Draw blood in a light blue-top tube containing 3.2% sodium citrate, mix gently by inverting 3-4 times. Centrifuge 15 minutes at 1500 g within one hour of collection. Using a plastic pipette, remove plasma, taking care to avoid the WBC/platelet buffy layer and place into a plastic vial. Centrifuge a second time and transfer platelet-poor plasma into a new plastic vial(s). Freeze immediately and transport on dry ice.

Room temperature: Unacceptable
Refrigerated: Unacceptable
Frozen: 30 days

Gross hemolysis • Grossly lipemic • Grossly icteric

Sets up 4 days a week.

Reports in 1 to 3 days.

Expected impact by therapeutic levels (potential interference depends upon drug concentration): Warfarin: no effect; Heparin (UFH or LMWH): no effect to decrease (UFH may decrease levels physiologically but no assay interference); Dabigatran or Argatroban (Thrombin Inhibitors): no effect; Rivaroxaban or Apixaban (Factor Xa Inhibitors): no effect.

80-120 % normal

Aids in characterization of Antithrombin deficiency (AT, previously referred to as Antithrombin III) which is associated with increased thrombotic risk. Type I deficiency is characterized by reduction in activity and antigen levels simultaneously. With type II deficiency, activity levels are lower in comparison to the antigen levels (dysfunctional protein). Acquired deficiency, more common than inherited defects, can occur due to: liver disease, nephrotic syndrome, heparin therapy, disseminated intravascular coagulation (DIC), sepsis, and L-asparaginase chemotherapy.

Anticoagulant interference: heparin therapy may lower AT levels. Other anticoagulants do not impact testing (warfarin, target specific anticoagulants such as Dabigatran, Argatroban, Rivaroxaban, Apixaban, Edoxaban).