Heparin Anti-Xa, Plasma

Test Code

894

Alias/See Also

Anti-10a
Anti-Xa
Fragmin (Dalteparin)
Heparin Anti-Xa Assay, Plasma
Lovenox (Enoxaparin)
Low-Molecular Weight Heparin Assay
Unfractionated Heparin Assay

Preferred Specimen

Specimen Type: Platelet-poor plasma
Collection Container/Tube: Light-blue top (3.2% sodium citrate)
Submission Container/Tube: Plastic vial
Specimen Volume: 1 mL

Minimum Volume

0.5 mL

Instructions

Collection Instructions: Spin down, remove plasma and spin plasma again

Additional Information: Double-centrifuged specimen is critical for accurate results as platelet contamination may cause spurious results.

Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)

Hemolysis	Mild OK; Gross Reject
Lipemia	Mild OK
Icterus	Mild OK
Other	Insufficiently filled tube

Methodology
Chromogenic

Reference Range

Check enoxaparin peaks for efficacy monitoring
Check enoxaparin troughs for safety monitoring

Peak Monitoring:
Peaks not recommended for prophylactic dosing, only for therapeutic dosing
Check peak anti Xa levels 3-4 hours after a dose.
Expected peak anti Xa levels for q12h dosing = 0.5 – 1 units/ml
Expected peak anti Xa levels for q24h dosing = 1-2 units/ml

Trough Monitoring:
Check trough anti Xa levels immediately prior to the next dose
Expected trough anti Xa levels = < 0.5 units/ml
Higher troughs suggest impaired clearance

Clinical Significance

Measuring heparin concentration:

-In patients treated with low-molecular-weight heparin preparations

-In the presence of prolonged baseline activated partial thromboplastin time (APTT) (eg, lupus anticoagulant, "contact factor" deficiency, etc)

-When unfractionated heparin dose needed to achieve desired APTT prolongation is unexpectedly higher (>50%) than expected

Not useful for monitoring therapy with the heparinoid "danaparoid"

Performed By
CoxHealth

Performing Laboratory
CoxHealth

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.