Heparin Assay (Anti-Xa)-LMWH

Test Code

HAAX

Alias/See Also

ANTI-Xa

CPT Codes
85520

Preferred Specimen

1 Blue

Minimum Volume

Blue tops must be filled to Minimum Fill Indicator Line on tube.

Other Acceptable Specimens

none

Instructions

Outreach clients should double-spin the blue top plasma, remove the plasma from the RBC button, and freeze in a polypropylene tube.

Transport Container

BLUE/1

Transport Temperature

Blue - RT Polypropylene tube - Frozen

Specimen Stability

Whole Blood - 1 hour RT Separated plasma - 2 hours at RT or 1 month frozen

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

Sample must be free of clots and hemolysis.

Methodology
Colorimetric

Setup Schedule

Daily 0600 - 1300

Report Available

Upon Completion of Analysis

Reference Range

SEE REPORT

Clinical Significance

The Anti-Xa Assay is intended for the quantitative determination of the plasma levels of low molecular weight heparin (LMWH) by the measurement of their anti-Xa activity on antithrombin in a competitive system using a synthetic chromogenic substrate.

The normal function of a molecule of factor Xa, as soon as it appears in plasma, is to cleave its natural substrate, Prothrombin, to generate thrombin, the enzyme responsible for the fibrin clot formation. In the presence of heparin, competition occurs between this mechanism and the inhibitory mechanism exerted by the heparin-antithrombin III complex, this inhibition being largely responsible for the action of heparin. The heparin-antithrombin complex is made up from the heparin and the antithrombin (AT) from the patient.

Unfractionated Heparin (UFH) and Low molecular weight heparins (LMWH) are used for the prevention and treatment of thromboembolic diseases. The quantitative determination of plasma UFH and LMWH levels are useful for monitoring treatment efficacy.

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.