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Test Code HEPTP Heparin Anti-Xa, Plasma

Useful For

Measuring heparin concentration:

-In patients treated with low-molecular-weight heparin preparations

-In the presence of prolonged baseline activated partial thromboplastin time (APTT) (eg, lupus anticoagulant, "contact factor" deficiency, etc)

-When unfractionated heparin dose needed to achieve desired APTT prolongation is unexpectedly higher (>50%) than expected

 

This test is not useful for monitoring therapy with the heparinoid "danaparoid."

Method Name

Chromogenic Method

Reporting Name

Heparin Anti-Xa, P

Specimen Type

Plasma Na Cit


Ordering Guidance


To test for the presence of inhibitors directed against factor X (FX), order 10INE / Factor X Inhibitor Evaluation, Plasma.



Specimen Required


Specimen Type: Platelet-poor plasma

Collection Container/Tube: Light-blue top (3.2% sodium citrate)

Submission Container/Tube: Plastic vial

Specimen Volume: 1 mL

Collection Instructions:

1. For complete instructions see Coagulation Guidelines for Specimen Handling and Processing.

2. Centrifuge, aliquot plasma, and centrifuge plasma again.

4. Aliquot plasma into a plastic vial leaving 0.25 mL in the bottom of centrifuged vial.

Additional Information: Double-centrifuged specimen is critical for accurate results as platelet contamination may cause spurious results.


Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Plasma Na Cit Frozen (preferred) 14 days
  Ambient  2 hours

Reject Due To

Gross hemolysis Reject
Gross lipemia OK
Gross icterus OK

Clinical Information

Heparins are sulphated glycosaminoglycans that inactivate thrombin, factor Xa, and several other coagulation factors; act by enhancing activity of the plasma coagulation inhibitor, antithrombin III; and prolong the activated partial thromboplastin time (APTT). The anti-Xa assay is the preferred method for monitoring low-molecular-weight heparin (LMWH) therapy because of reduced sensitivity of APTT. Heparin is absent in normal plasma. The heparin level obtained must be analyzed in the context of the treatment given to the patient (type of heparin, dosage, administration mode, time of sampling, etc) and the desired therapeutic effect. It is clinically recommended that platelet counts be monitored frequently in patients receiving unfractionated heparin or LMWH in order to detect heparin-induced thrombocytopenia.

Reference Values

Adult Therapeutic Range

UFH therapeutic range: 0.30-0.70 IU/mL

(6 hours following initiation or dose adjustment)

LMWH therapeutic range: 0.50-1.00 IU/mL for twice daily dosing*

LMWH therapeutic range: 1.00-2.00 IU/mL for once daily dosing*

LMWH prophylactic range: 0.10-0.30 IU/mL

 

*Sample obtained 4 to 6 hours following subcutaneous injection

Day(s) Performed

Monday through Sunday

Report Available

Same day/1 day

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information

85520