Arixtra (Fondaparinux) Assay


Sunquest Code:ARIX  
Epic Code:LAB3292Epic Name:Arixtra Level
Synonyms:Fondaparinux Assay
Methodology:Xa assay for Arixta
CPT Code:85520
Turnaround Time:Turnaround time is 4-8 hours if received during lab hours (see Associated Links). With pre-notification, stats are done within 1 hr after receipt in the laboratory.
Special Instructions:See link to Specimen Collection and Processing for Coagulation Specimens.
Associated Links:

Specimen Collection and Processing for Coagulation Specimens



Collection Instructions

Specimen:Blood
Optimal Volume:2.7 mL (in 3 mL tube) - filled to fill line on the tube.
Minimum\Peds Volume:1.8 mL (in 2 mL tube) - filled to fill line on the tube.
Collection Instructions:See link to Specimen Collection and Processing for Coagulation Specimens.
Causes for Rejection:Underfilled tubes or clotted specimens.


Processing and Shipping

Specimen Processing:See link to Specimen Collection and Processing for Coagulation Specimens.
Shipping Instructions:See link to Specimen Collection and Processing for Coagulation Specimens.
Test Performed at or Referral Lab Special Coagulation  (UMMC-East Bank)


Interpretive

Therapeutic Range:

The therapeutic anti-Xa range for fondaparinux has not been established. In patients treated with 2.5 mg fondaparinux daily the peak steady-state plasma concentration is on average 0.39 to 0.50 mcg/mL approximately 3 hours post-dose and the minimum steady-state plasma concentration is 0.14 to 0.19 mcg/mL. In patients treated with 5 mg (body weight <50 kg), 7.5 mg (body weight 50-100 kg), and 10 mg (body weight >100 kg) fondaparinux once daily, the mean peak steady-state plasma concentration is approximately 1.20 to 1.26 mcg/mL and the mean minimum steady-state plasma concentration is approximately 0.46 to 0.62 mcg/mL.

[Arixtra Prescribing Information version 9/2013. GlaxoSmithKline, Research Triangle Park, NC and Garcia et al. Chest 2012; 141:e24s-e43S]

 

 

Use:Fondaparinux is a synthetic anticoagulant with selective inhibition of activated factor X (factor Xa). Fondaparinux induces a conformational change in antithrombin and increases its affinity for factor Xa. Inhibition of factor Xa leads to decreased thrombin generation and thrombus development. Fondaparinux has a half-life of approximately 17 hours which allows once-daily dosing. It is almost completely excreted by the kidneys. Fondaparinux is approved for the prophylaxis and treatment of venous thromboembolic events. Laboratory monitoring of Fondaparinux is possible by utilizing factor Xa inhibitory activity of the drug. Anti-Xa assay (used for monitoring heparin) is modified by using a standard curve constructed with Fondaparinux.


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