| Primary Name | Anti-Xa |
| Synonym | Unfractionated heparin anti-Xa assay |
| Synonym | Low molecular weight heparin anti-Xa assay |
| Contraction | Heparin assay |
| Contraction | UFH anti-Xa assay |
| Contraction | LMWH anti-Xa assay |
| UAB Procedure Number | 2500670 |
| CPT Code | 85520 |
| Specimen | Collect one (1) blue-stopper tube (3.2% sodium citrate), filled to specified volume. Specimen will be rejected if underfilled. |
| Specimen Management | Hard centrifuge and separate the plasma within one hour. The specimens MUST be double spun to assure platelet poor plasma. Transport or ship at ambient temperature. • If plasma cannot be shipped within one hour of collection, freeze at -70°C and ship on ice or dry ice. |
| Specimen Accepted | Daily including weekends |
| Times Available | All times. |
| Test Performed | All times. |
| Available Stat? | Yes. |
| Description | The anti-Xa test is the most accurate assay for monitoring unfractionated heparin therapy and is the only assay available for monitoring low molecular weight heparin (Lovenox®). The anti-Xa level applies to patients anticoagulated with heparins (unfractionated and low molecular weight heparin). |
| Critical Value | > 1.0 anti-xa heparin units per mL plasma |
| Therapeutic Range | *IV therapeutic unfractionated heparin: 0.3 - 0.7 anti-Xa units per mL plasma. *Prophylactic unfractionated heparin: 0.2-0.4 anti-Xa units per mL plasma. *Low molecular weight heparin (Lovenox, enoxaparin): 0.5 to 1.0 anti-Xa units per mL plasma for therapy when injected twice a day. Draw four hours after injection. *Low molecular weight heparin (Lovenox, enoxaparin): 1.0 to 2.0 anti-Xa units per mL plasma for therapy when injected once a day. Draw four hours after injection. *Low molecular weight heparin (Lovenox, enoxaparin): 0.2 to 0.4 anti-Xa units per mL plasma for prophylaxis. Draw four hours after injection. |
| Follow-up Test | -- |
| Associated With | Heparin therapy |
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