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Test Compendium


Test Code

  • 6716

Test Synonym

  • Heparin Anti-XA (Low Molecular Weight Heparin), Heparin Anti-XA (Unfractionated Heparin), LMWH, Low Molecular Weight Heparin , UFH


  • 2 mL

Minimum Volume

  • 1 mL

Specimen Requirements

  • Plasma


  • Transfer Tube- Frozen- Plasma


  • Frozen

CPT Codes

  • 85520
    *The CPT codes provided are based on AMA guidelines and are provided for informational purposes only. CPT coding is the responsibility of the billing entity. Please direct any questions regarding the CPT coding to the payer being billed.

Special Instructions

  • 2 mL FROZEN Citrated Plasma

Additional Information

  • Blood should be collected in a blue-top tube containing 3.2% buffered sodium citrate.[1] Evacuated collection tubes must be filled to completion to ensure a proper blood to anticoagulant ratio.[2,3] The sample should be mixed immediately by gentle inversion at least 6 times to ensure adequate mixing of the anticoagulant with the blood. A discard tube is not required prior to collection of coagulation samples.[4,5] When noncitrate tubes are collected for other tests, collect sterile and nonadditive (red-top) tubes prior to citrate (blue-top) tubes. Any tube containing an alternate anticoagulant should be collected after the blue-top tube. Gel-barrier tubes and serum tubes with clot initiators should also be collected after the citrate tubes. Centrifuge and (using a transfer pipette) carefully remove the plasma without disturbing the cells. Transfer the plasma into a plastic transport tube with screw cap. The specimen should be FROZEN immediately and maintained frozen until tested. To avoid delays in turnaround time when requesting multiple tests on frozen samples, please submit separate frozen specimens for each test requested. Heparin anti-Xa levels should be drawn six hours after initiation of unfractionated heparin therapy or change in dose, whereas, with low molecular weight heparin, levels should be drawn six hours after administration when given once daily and three to four hours when administered twice daily. Fondaparinux levels should be measured three hours postadministration.

Specimen Stability

  • AMBIENT: unstable REFRIGERATED: unstable FROZEN: stable