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HEPARIN ANTI-XA
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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 six 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 carefully remove the plasma using a plastic transfer pipette, being careful not to disturb the cells. Transfer the plasma into a LabCorp PP transpak frozen purple tube with screw cap (LabCorp N° 49482). Freeze immediately and maintain 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.
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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 six 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 carefully remove the plasma using a plastic transfer pipette, being careful not to disturb the cells. Transfer the plasma into a LabCorp PP transpak frozen purple tube with screw cap (LabCorp N° 49482). Freeze immediately and maintain 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.
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Test Code
117101
CPT Codes
85520
Preferred Specimen
"Plasma, frozen
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Minimum Volume
"1 mL
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Instructions
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If the patient's hematocrit exceeds 55%, the volume of citrate in the collection tube must be adjusted. Refer to Coagulation Collection Procedures for directions. 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.
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If the patient's hematocrit exceeds 55%, the volume of citrate in the collection tube must be adjusted. Refer to Coagulation Collection Procedures for directions. 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.
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Transport Container
"Blue-top (sodium citrate) tube
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Transport Temperature
Freeze
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
"Gross hemolysis; clotted specimen; frozen specimen thawed in transit; improper labeling
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Methodology
"The heparin anti-Xa assay is based on the ability of heparin to inhibit the activity of activated factor X (Xa) in the reagent. The reagent includes excess antithrombin, making the heparin in the sample the rate-limiting reagent for Xa inhibition. Heparin in the patient sample inhibits the enzymatic conversion of a Xa-specific chromogenic substrate to colored product by factor Xa. Standard curves are created using multiple concentrations of UFH and LMWH and are used to calculate concentration in the patient plasma. "
Reference Range
"Reference intervals indicate therapeutic levels.
• Unfractionated heparin (UFH): 0.30-0.70 IU/mL
• Low molecular weight heparin (LMWH): 0.50-1.00 IU/mL
- Twice daily dosing: 0.6-1.1 IU/mL
- Once daily dosing: 1.0-2.0 IU/mL
• Fondaparinux: 0.39-0.5
• Unfractionated heparin (UFH): 0.30-0.70 IU/mL
• Low molecular weight heparin (LMWH): 0.50-1.00 IU/mL
- Twice daily dosing: 0.6-1.1 IU/mL
- Once daily dosing: 1.0-2.0 IU/mL
• Fondaparinux: 0.39-0.5
