Heparin Anti Xa Assay




Test Mnemonic

HEPASY

CPT Codes

  • 85520 - QTY (1)

LOINC ®

3217-7

Aliases

  • Factor Xa Inhibition/Heparin Assay
  • Heparin Assay

Performing Laboratory

Cleveland Clinic Laboratories


Specimen Requirements

Volume Type Container Collect Temperature Transport Temperature Special Instructions
1 mLPlatelet-poor plasmaSodium citrate (Lt. Blue) Frozen 

Minimum Specimen Requirements

Volume Type Container Collect Temperature Transport Temperature Special Instructions
0.5 mL    A minimum of 0.5ml of platelet-poor plasma is needed; therefore, draw no less than 1.5ml whole blood in a 1.8ml sodium citrate tube.

Stability

Environmental Condition Description
AmbientCentrifuge within one hour of phlebotomy and test or freeze platelet poor plasma within four hours.
Frozen2 weeks at less than or equal to -20 degrees C. 6 months at less than or equal to -70 degrees C.
RefrigeratedUnacceptable

Days Performed

Sun - Sat

Turnaround Time

4 hours

Methodology

Name Description
Chromogenic 

Reference Range

Heparin Anti Xa
Sex Age From Age To Type Range Range Unit
   Years99 YearsNormalTherapeutic range: 0.3 - 0.7 (standard nomogram)IU/mL
   Years99 YearsNormal< 0.10IU/mL
   Years99 YearsNormalStroke or low dose protocol: 0.2 - 0.5 (see EPIC for detailed nomogram)IU/mL

Special Info

3.2% sodium citrate is the preferred anticoagulant recommended by CLSI. Patient samples should be centrifuged by the laboratory < 1 hour from collection time to prevent falsely decreased Heparin Anti Xa values due to heparin neutralization by in vitro release of platelet factor 4. Samples that are centrifuged > 1 and < 4 hours from collection will have the following comment attached: Interpret with caution. Sample centrifuged greater than 1 hour from collection time. According to Clinical and Laboratory Standards Institute guidelines, results could be falsely decreased due to heparin neutralization by in vitro release of platelet factor 4. Suggest correlation with clinical findings and redraw if indicated.

Clinical Info

For monitoring unfractionated heparin therapy. This assay may be useful in monitoring heparin therapy in individuals where the APTT cannot be used due to basal APTT elevation, such as those with a lupus anticoagulant.