Days Set Up
Daily, 24 hours
Analytic Time

2 hours

MiChart Code
FONDAPARINUX (Arixtra), Anti-Xa
Soft Order Code

Test Updated:


Factor Xa Inhibition
Anti-Xa Arixtra
Chromogenic Xa
Xa Chromogenic
Anti-Xa Fondaparinux
Coagulation Factor Xa Inhibition
Arixtra Anti-Xa
Factor 10a Inhibition
Anti-10a Arixtra

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Test Overview

Test Methodology

Chromogenic Substrate Assay

Test Usage

Used to monitor treatment with Arixtra (fondaparinux) when clinically indicated. Dosing protocols for DVT prophylaxis and treatment of DVT/PE have been validated by empiric clinical trials. Clinical monitoring with Arixtra levels is not necessary for most patients.

Reference Range

Normal individuals have no Arixtra activity.
Expected Therapeutic Ranges:
DVT prophylaxis (Arixtra 2.5mg qd)
3 hours after dose: 0.39-0.50mg/L
Trough: 0.14-0.19 mg/L drawn just prior to next dose.
Treatment of thrombosis (Arixtra 5-10mg qd)
3 hours after dose: 1.20-1.26 mg/L
Trough: 0.46-0.62 mg/L drawn just prior to next dose.

* Reference ranges may change over time. Please refer to the original patient report when evaluating results.

Specimen Requirements

Collection Offsite

The sample should be drawn 3 hours after injection of drug in order to compare to published peak levels. Collect specimen in a blue top (citrate 3.2%) tube. Mix by inversion. Specimen should arrive at lab within 3 hours of collection; transport at room temperature. Alternatively, centrifuge, aliquot plasma into a plastic vial, and freeze the specimen within 4 hours of collection. Transport frozen specimen on dry ice. Collection of the blood through lines that have been previously flushed with heparin should be avoided. If the blood must be drawn through a VAD (vascular access device), the line should be flushed with 5 mL of saline and the first 5 mL of blood or six dead space volumes of the VAD discarded.

Blue Top Tube
Normal Volume
Full 2.7mL tube or 1mL plasma aliquot
Minimum Volume
Full 1.8mL tube or 1mL plasma aliquot

Billing Information

CPT Code
Pro Fee Code

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Our High Standard

Quality that sets us apart

As the reference laboratory division of Michigan Medicine's Department of Pathology, MLabs shares the institution's commitment to applying established quality principles to clinical laboratory testing. Like other large organizations in complex, consequential fields, we rely on an established approach to monitor quality throughout the testing process.