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Jan 23, 2017

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Heparin Level by anti-Xa

Heparin Level by anti-Xa (XLMWH) Coagulation Lab Test

Name: Heparin Level by anti-Xa

Test Name: Heparin Level by anti-Xa

Health Link Test Code: XLMWH

LIS Test Code: HEPRN

CPT Code(s): 85520

Methodology: Chromogenic Anti-Xa Assay

Clinical Information:

Note: This is NOT a Factor X assay. The plasma level of unfractionated heparin (UFH) or low molecular weight heparin (LMWH) is determined by the measurement of anti-Xa activity.

Days Performed: Daily, 24 hours.

In-Lab Turnaround Time: 4 hours.

Stat In-Lab Turnaround Time: 1 hour.

Specimen: Blood

Collection Container: Light blue top (3.2% NaCitrate)

Collection Instructions:

Do NOT draw through a line containing heparin (this assay measures any type of heparin present in the sample, including line contamination). The venipuncture MUST be atraumatic to avoid hemolysis and contamination with tissue factors and platelets. Tube must be allowed to fill completely.

 

Please indicate patient history and type of heparin the patient is receiving. For Low Molecular Weight Heparin (LMWH), collect specimen as close as possible to 4 hours post-dosing.

 

If unable to collect 1.8 ml tube (pediatrics only) please call UWHC Coagulation Lab at (608)263-9617 or UWHC Special Coagulation Lab at (608) 263-5005 for alternate tube and instructions.

Collection Volume: Full 3.5 mL tube

Pediatric Collection Volume: Pediatric tube filled to fill mark

Stability Ambient:

1 hour off cells

Stability Refridgerated:

Not acceptable

Stability Frozen:

2 weeks at -20°C; 6 months at -70°C

Sample Analyzed: Plasma

Testing Volume: 1 mL

Pediatric Testing Volume: 0.3 mL

Specimen Processing:

Centrifuge specimen within one hour of collection to yield platelet poor plasma (platelet count of plasma should be less than 10 K/µL). Separate plasma and transfer to plastic tube or vial. Freeze plasma at -20°C or below.

Specimen Transport:

Transport whole blood specimen at room temperature to UWHC Hosptial Laboratory within 1 hour of collection. See Specimen Processing for instructions if transport criteria are not met. Transport frozen plasma aliquot on dry ice to laboratory.

Unacceptable Criteria:

Hemolyzed specimens, clotted specimens, partially filled tubes and whole blood specimens greater than 1 hour old when received by the laboratory are not acceptable.

Interpretation:

If sample was collected through a line, this method is unable to distinguish heparin level in the sample from possible line contamination.

 

This method does not add antithrombin to the testing.

 

Recommended therapeutic ranges:

Standard (unfractionated) heparin: 0.3 - 0.7 anti-Xa IU/mL

 Reference values have not been established for patients who are less than 8 weeks of age.

Low molecular weight heparin (LMWH): varies with the type and manufacturer, but is typically between 0.5-1.1 anti X-a IU/mL. For LMWH, collect specimen as close to FOUR hours post-dosing as possible. Recommended therapeutic range is valid for twice-daily dosing. Levels will be higher for once daily dosing.

 

Reference: Supplement to Sept 2008, Chest, vol 133, number 6.

 

Contact UWHC Special Coagulation at (608) 263-5005 for more information.

Interpretation Type: Expected Results

Additional Information:

NOTE: This is NOT a Factor X assay. 

 

If sample is collected through a line, this method is unable to distinguish heparin level in the sample from possible line contamination.

Recommended therapeutic ranges:

Standard (unfractionated) heparin: 0.3 - 0.7 anti Xa IU/mL

Low molecular weight heparin (LMWH): varies with the type and manufacturer, but is typically between 0.5 - 1.1 anti Xa IU/mL. For LMWH, collect specimen as close to FOUR hours post-dosing as possible. Recommended therapeutic range is valid for twice-daily dosing. Levels will be higher for one daily dosing.

Reference: Supplement to Sept 2008. Chest, vol 133, number 6.