Sign in →

Test Code LMWHXA or LAB3474 Low Molecular Weight Heparin Anti-Xa Assay

Important Note

This assay should only be ordered when monitoring levels of low molecular weight heparin.

If monitoring levels of Unfractionated Heparin, please order the Unfractionated Heparin Anti-Xa assay.

Specimen Requirements

Specimen Type:

Whole Blood

Container Type:

Blue top: 2.7 mL or 1.8 mL

Optimal Collection Volume:
  • 2.7 mL in solid blue top tube or 1.8 mL in clear blue top tube.  The correct fill volume is indicated by the etched line on the tube.
  • Click here to view the specimen collection guide for blue top (citrate) tubes.

Collection Instructions:
  1. Do not draw from an arm with a heparin lock.
  2. Gently invert 5 to 10 times to mix blood.
  3. If collected through a blood collection set (butterfly), a discard tube must first be drawn to eliminate dead space from tubing.  

Specimen Transport Temperature:
  • Room temperature for up to 4 hours. If testing is delayed, separate plasma and freeze (see outpatient collection instructions below).
  • Specimens cannot be refrigerated

Processing Instructions:
  1. Centrifuge sample within 4 hours of collection. Platelet-poor plasma must be obtained per laboratory procedure.
  2. If testing will be delayed >4 hours from collection, aliquot plasma into a separate vial and freeze immediately.

Outpatient collections

  1. Spin down the sample, remove plasma, and spin plasma again to obtain platelet-poor plasma.
  2. Separate the platelet-poor plasma into a screw-top vial.
  3. Freeze plasma immediately.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Specimen Stability

Specimen Type

Temperature

Time

Whole blood

Room Temperature

4 hours

Platelet Poor Plasma

Room Temperature

4 hours

Platelet Poor Plasma

Frozen at - 20 C

2 weeks

Specimen Rejection Criteria

  • Tube underfilled
  • Refrigerated specimen
  • Clotted specimen
  • Specimen not processed within four hours of collection

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)

Not useful for monitoring therapy with the heparinoid "danaparoid".

Methodology

The Liquid Anti-Xa kit (ACL TOP) is a 1-stage chromogenic assay based on a synthetic chromogenic substrate and on factor Xa inactivation. (Package insert HemosIL Liquid Anti-Xa)

Reference Ranges

Therapeutic Range

  • 0.50-1.00 units/mL for twice daily dosing
  • 1.00-2.00 units/mL for once daily dosing

 

Prophylactic Range

Sample is obtained 3-5 hours following subcutaneous injection */we are verifying if 3-5 or 4-6 is the correct range*/

  • 0.20-0.50 units/mL

 

Day(s) Performed

24/7

Expected TAT

Same day

Performing Laboratory

Bronson Laboratory, Coagulation - Kalamazoo and Battle Creek

Sample Retention Time

24 hours

CPT Code

85520

Related Tests