Heparin (10a) Level

Sunquest Code:AXA  
Epic Code:LAB3301Epic Name:Heparin 10A Level
Synonyms:Heparin Xa; Heparin Level; Lovenox; Enoxaparin; Anti 10A; Anti Xa
Methodology:Chromogenic (synthetic substrate) activity assay
Turnaround Time:Performed and reported 24 hours/day.
Associated Links:

Specimen Collection and Processing for Coagulation Specimens

Collection Instructions

Optimal Volume:2.7 mL (in 3 mL tube) - filled to fill line on the tube
Minimum\Peds Volume:1.8 mL (in 2 mL tube) - filled to fill line on the tube
Container:Blue Na Citrate, 3.2% - fill to fill line on tube
Collection Instructions:If the patient's hematocrit is >55%, contact laboratory to obtain a special tube. If using a butterfly needle, a waste tube must be collected before the blue top.
After Care:If the patient has a coagulation abnormality, apply direct pressure to the puncture site for 10 minutes; apply a pressure dressing. Instruct the patient to leave the bandage on for 12 hours.
Causes for Rejection:Underfilled tubes, overfilled tubes, clotted specimens, specimen collected in 3.8% buffered citrate.
Grand Itasca: Whole blood specimen greater than 4 hours old or not processed appropriately within 1 hour of collection.
All other Fairview sites: Whole blood specimen greater than 2 hours old or not processed appropriately within 1 hour of collection.

Processing and Shipping

Specimen Processing:
  • Grand Itasca: Whole blood must be processed within 1 hour; processed specimen can be stored unopened at room temperature for up to 4 hours. If >4 hours, aliquot off and freeze at -20°C for up to 2 weeks, or -70°C for up to 6 months.
  • All other Fairview sites: Must be processed within 1 hour of collection. See Associated Links for additional processing instructions.
Shipping Instructions:Ship processed plasma on dry ice. Must arrive within 48 hours.
Test Performed at or Referral Lab Coagulation  (Fairview Range - FRMC, UMMC-East Bank, Fairview Lakes - FLMC, Fairview Ridges - FRH, Fairview Northland - FNMC, Fairview Southdale - FSH, UMMC/UMMCH-West Bank, Grand Itasca GICH)


Critical Range:Greater than 1.0 IU/mL; does not apply if patient is on low molecular weight heparin.
If the patient is receiving unfractionated heparin and the result is greater than 1.10 IU/mL, the result should be considered as >1.10 IU/mL. The analytical measurement limit for unfractionated heparin is up to 1.10 IU/mL. This does not apply to patients on low molecular weight heparin. The analytical measurement limit for low molecular weight heparin is up to 2.00 IU/mL.
Therapeutic Range:

If collected 4-6 hours after administration:

  • Enoxaparin: If administered twice daily with dose 1 mg/kg: 0.60-1.0 IU/mL. If administered only once daily with a dose of 1.5 mg/kg: 1.0-2.0 IU/mL
  • Unfractionated heparin: "Low intensity" for CV, vascular and thrombolytic therapy: 0.15-0.35 IU/mL; "high intensity" for DVT and PE: 0.3-0.7 IU/mL


Use:Estimate the concentration of physiologically active heparin anticoagulant (anti-Factor Xa activity) in plasma.

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