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Test Code ANTIXA Heparin Anti Xa Assay, Plasma, LAB2513

Additional Codes



Chromogenic assay

Performing Laboratory

St. Luke's Hospital Cedar Rapids

Specimen Requirements


Preferred: Full blue-top (sodium citrate) 1.8 mL tube-Hemolyzed or short draw specimen is not acceptable.
Specimen Volume: 0.5 mL sodium citrate plasma

Stability: Centrifuged specimens at 2-4°C or at 15-25°C must be tested within 4 hours of specimen collection.

Collection Instructions: Centrifuge immediately after draw. Forward promptly. If there is a delay in transport of >4 hours or if mailing time exceeds 4 hours, spin down, remove plasma from cells and freeze immediately in plastic vial. Send specimen frozen. Specimen stability is 1 month at -20° C.


NOTE:  Patients with a hematocrit of> 55% must be recollected using an altered amount of sodium citrate.

Reference Values

0.30-0.70 iu/mL


Critical value:  ≥1.04 IU/mL

Day(s) Test Set Up

Monday through Sunday

Test Classification and CPT Coding


Useful For

Useful in monitoring Unfractionated Heparin used for heparin therapy

Report Available

STAT within 1 hour of receipt. Routine within 2 hours of receipt.