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Test Name:

ANTITHROMBIN ACTIVITY

Test Code:

2187015

Alias:

LAB311

CPT Code(s):

85300

Preferred Specimen:

2.0 mL plasma

Container:

2 - Sodium Citrates (lt blue)

Minimum Volume:

2 - full Sodium Citrates (lt blue)

Collection Instructions:

Tube must be filled to completion to ensure a proper blood to anticoagulant ratio. Mix tubes gently by inverting 5-10 times immediately after filling. Centrifuge for 15 minutes within 1 hour of collection. Using a plastic pipette, remove plasma taking care to avoid the WBC/platelet buffy layer and transfer plasma into a properly labeled transfer tube. Centrifuge the transferred plasma a second time and transfer platelet poor plasma into a new properly labeled purple frozen transport tube. Label tube as "platelet poor". Freeze immediately.

*Original tube is not needed if plasma is sent frozen*

Transport Temperature:

Plasma: Frozen
Original tubes: Room temperature

Stability:

Frozen: 14 days

Rejection Criteria:

Refrigerated or room temperature specimens

Limitations:

If the patient's hematrocrit exceeds 55%, the volume of citrate in the collection tube must be adjusted.

Additional Information:

Antithrombin levels are low in neonates/infants and increase to adult levels by approximately 1 year of age; levels are then slightly higher than in adults up to age 16 years.

Schedule:

Set up: Mon-Fri; Results in 1-3 days

Method:

Chromogenic Substrate

Clinical Significance:

Antithrombin (AT) or Heparin Cofactor I is the major inhibitor of blood coagulation and is essential for effective heparin therapy. By inhibiting the coagulation proteases, especially thrombin, FXa and FIXa, AT prevents uncontrolled coagulation and thrombosis. Liquid Antithrombin can be used to exclude or diagnose hereditary deficiency in patients with a tendendency toward thromboembolism, in pre-operative stages, before prescription of oral contraceptives, DIC, nephritic syndromes, liver disease, and in therapy with heparin or antithrombin concentrates.

Use:

updated 2/25/25

Reference Ranges:

Refer to patient report.

Reference Range Table

Result	Units	Gender	Age	Range
Antithrombin	% Activity	Both	0 Year - 999 Year	91.0-132%

Health Lab Test Code Build Information

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The CPT codes included in this publication are in accordance with Current Procedural Terminology, a publication of the American Medical Association. CPT codes are provided here for the convenience of our clients; however, correct coding often varies from one carrier to another, and HealthLab may bill specific carriers using codes other than those shown. Clients who bill for services should verify the code(s) with the applicable payor to confirm that their use is appropriate in each case.

Reference Range Table

Health Lab Test Code Build Information

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