Test Code: Xa Preferred Name Heparin assay

1 hour
As required
Medicare Item

Test Tubes

ImageSpecimen TypeSpecimen VolumeTube Type
Blood (adult)2.7 mLSodium Citrate 2.7 mL (Solid Pale Blue Top)
Blood (paediatric)1.8 mLSodium Citrate 1.8 mL Paed (Clear/Pale Blue Inner)
Blood (Neonate)1.0mlSodium Citrate 1.0 mL Neonate (Pale Blue Top)


Specimens must be stored at room temperature and transported to Laboratory in a RED bag ASAP. (Maximum delay to testing laboratory must not exceed 1hr) Please ring Haematology on 31638665 if problems are anticipated.
Please ask the patient what anticoagulants they are on, the current dose, and time of last dose. Record on request form.
Accurate filling of specimen tube is essential.
Due to a small specimen viability window, patients for this test should be booked close to the courier runs.
Anti-Xa testing needs to be sent to the laboratory in a RED specimen bag.
Anti-Xa levels should be collected 3-4 hours post-dose of Low Molecular Weight Heparin (e.g. Clexane and Fragmin).
Anti Xa levels should be collected 4 hours post dose of Unfractionated Heparin (UFH) or commencing the end of the infusion (trough level).


When LMWH is administered, patients with extreme body weight, renal insufficiency, pregnant women and small children probably need monitoring of anti-Xa levels

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