2 hours
Test Updated:
Factor Xa Inhibition
Anti-Xa Arixtra
Chromogenic Xa
Xa Chromogenic
Anti-Xa Fondaparinux
Fondaparinux
ARIXTRA
Coagulation Factor Xa Inhibition
Arixtra Anti-Xa
ARIX
Factor 10a Inhibition
Anti-10a Arixtra
Looking to order a test?
We’ve provided helpful links to make ordering easy.
Find a RequisitionAll specimens should be accompanied by a requisition.
Submitting SpecimensLearn about how to properly label and where to ship specimens.
Order Kits and SuppliesMLabs provides all the supplies necessary for the collection of specimens.
Test FAQVisit our provider FAQ and learn about common questions to ordering tests.
Test Overview
Chromogenic Substrate Assay
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.
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
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.