Antithrombin III Activity

Message

Collect at Main Hospital or Front Desk Lab Only

Test Code

LAB311

Quest Code

216

Alias/See Also

AT3A; ANT3A

CPT Codes
85300

Preferred Specimen

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

Minimum Volume

0.5 mL

Instructions

Centrifuge light blue-top tube for 15 minutes at approximately 1500 g 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 a second time and transfer platelet poor plasma into a new plastic vial. Plasma must be free of platelets (<10,000/mcL). Freeze immediately and ship on dry ice.

Transport Temperature

Frozen

Specimen Stability

Room temperature: Unacceptable
Refrigerated: Unacceptable
Frozen: 30 days

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

Hemolysis • Received room temperature • Received refrigerated

Methodology
Chromogenic Substrate

Setup Schedule

P.M.

Limitations

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): may falsely increase; Rivaroxaban or Apixaban (Factor Xa Inhibitors): no effect.

Reference Range

1 day-1 month	41-108 % normal
31 days-2 months	50-120 % normal
3-5 months	73-120 % normal
≥6 months	80-135 % normal

Clinical Significance

Aids in the detection of hypercoagulable states associated with venous thrombotic episodes. May be useful in patients who appear to be hyporesponsive to heparin.

Performing Laboratory
Quest Diagnostics Nichols Institute
33608 Ortega Highway
San Juan Capistrano, CA 92675-2042

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.