Fondaparinux Assay
Test Mnemonic
FONDXA
CPT Codes
- 85520 - QTY (1)
Aliases
- Arixtra
- Fondaparinux Anti-Xa assay
Performing Laboratory
Cleveland Clinic Laboratories
Specimen Requirements
| Volume | Type | Container | Collect Temperature | Transport Temperature | Special Instructions |
|---|---|---|---|---|---|
| 1 mL | Plasma | Sodium citrate (Lt. Blue) | Ambient | Centrifuge, aliquot and freeze ASAP. |
Minimum Specimen Requirements
| Volume | Type | Container | Collect Temperature | Transport Temperature | Special Instructions |
|---|---|---|---|---|---|
| 1 mL | 2 ml plasma is recommended if repeat testing is required |
Stability
| Environmental Condition | Description |
|---|---|
| Ambient | Centrifuge and separate the plasma. Plasma stable for 4 hours at room temperature |
| Refrigerated | Unacceptable |
| Frozen | Centrifuge, aliquot and freeze plasma. Plasma frozen at -20° C stable for 1 month and frozen at -70°C stable for up to 6 months. |
Days Performed
Sun - Sat
Turnaround Time
4 hours
Methodology
| Name | Description |
|---|---|
| Chromogenic |
Reference Range
| Fondaparinux | |||||
|---|---|---|---|---|---|
| Sex | Age From | Age To | Type | Range | Range Unit |
| Refer to report |
Special Info
3.2% sodium citrate is the preferred anticoagulant recommended by CLSI.
Clinical Info
Fondaparinux (Arixtra) is an indirect synthetic factor Xa inhibitor based on the active pentasaccharide site of heparin mucopolysaccharides, and is utilized as an anticoagulant drug for treatment or prevention of thromboembolic events. Its antithrombotic mechanism is antithrombin-mediated selective inhibition of factor Xa after binding fondaparinux with antithrombin. However, fondaparinux does not inactivate thrombin and has no effect in platelet function or fibrinolysis. The Fondaparinux Activity assay allows the determination of the plasma levels of fondaparinux by measuring its acceleration of inhibition of activated factor X using a chromogenic substrate method using calibration curve calculated with a commercial Arixtra (fondaparanux) calibrator. This assay cannot be used to monitor patients receiving unfractionated or low molecular weight heparins. Fondaparinux has a half life of approximately 17-21 hours in healthy normal individuals, however, it can be prolonged in patients with renal impairment because fondaparinux is mainly eliminated in urine. While patients treated with fondaparinux are not typically monitored, there is clinical need for monitoring and therapeutic assessment in patients with bleeding or thrombotic complications. In patients undergoing treatment with fondaparinux sodium injection 2.5 mg, once daily, the peak steady-state plasma concentration is, on average, 0.39 to 0.50 mg/L and is reached approximately 3 hours post-dose. In these patients, the minimum steady-state plasma concentration is 0.14 to 0.19 mg/L. In patients with symptomatic deep vein thrombosis and pulmonary embolism undergoing treatment with fondaparinux sodium injection 5 mg (body weight <50 kg), 7.5 mg (body weight 50 to 100 kg), and 10 mg (body weight >100 kg) once daily, the body-weight-adjusted doses provide similar mean steady-state peaks and minimum plasma concentrations across all body weight categories. The mean peak steady-state plasma concentration is in the range of 1.20 to 1.26 mg/L. In these patients, the mean minimum steady-state plasma concentration is in the range of 0.46 to 0.62 mg/L. (Prescribing information for Arixtra from GlaxoSmithKline, Oct 2010