PatientsVisitorsLocations & ServicesAbout the RegionJoin Our TeamPhysicians
Find:  Locations | Services
Pathology and Laboratory Medicine HomeTest and Services CatalogueTransfusion Medicine Product CataloguePolicy and ProcedureJob AidsSpecimen Collection and TransportRequisitionsAntibiogramsGenetic Testing and Molecular GeneticsMicrobiology EssentialsTransfusion EssentialsReference RangesLaboratory SuppliesAcute Care SCM GuidelinesContact InformationPhysician Access to Patient ResultsNew Clinic or Provider Information Changes
Pathology and Laboratory Medicine
Test Catalogue


Hematology - Special Coagulation

​Ordering Recommendation

  • ​ ​To monitor the peak level of low molecular weight heparin the specimen shall be drawn four hours post dose

Specimen Requirements​ ​

  • ​Whole blood
  • ​Preferred Collection Container: BLUE plastic (3.2% Buffered Na citrate)
  • Collection tube must be filled until the vacuum on the tube is completely exhausted to maintain an anticoagulant : blood ratio of 1:10
​Collection Procedure
​Required Volume
  • ​Optimal Volume: 2.7 mL 3.2% Buffered Na Citrate or 1.0mL platelet poor Sodium Citrate plasma
  • Minimum Volume: 1.8 ml 3.2% Buffered Na Citrate or 0.5 mL platelet poor Sodium Citrate plasma
    (Submitting the minimum volume makes it impossible to repeat the test or perform confirmatory/reflex testing. In some situations, a minimum volume may require a second collection.)
  • ​Whole blood specimen shall be received at RUH Coagulation Laboratory and SPH Coagulation Laboratory within 2 hours of collection
  • Specimen is discarded after reporting.  If an extra specimen is collected it is retained for 3 months
Grounds for Rejection​

Testing Information​ ​

  • ​24 hours a day, 7 days a week
Testing Site​
  • ​RUH Coagulation Laboratory
  • SPH Coagulation Laboratory
Results Reporting​
  • ​Turn around time – maximum 24 hours a day, 7 days a week
Clinical Interpretation
  • ​Useful for assessing the activity of low molecular weight Heparin.  In most cases monitoring of anti-factor Xa activity levels is not required when patients are on low molecular weight Heparin.  Exceptions include cases where the patient is a child, is pregnant, is morbidly obese, has renal insufficiency, recent or impending surgical procedures, trauma, ischemic stroke, a history of GI bleeding or patients receiving recent or concurrent anticoagulants if clinical judgement indicates high bleeding risk.
  • Caution should be exercised when interpreting results from a line draw. Any heparin contamination or dilution will affect the results.
Alternate Test Names​
  • ​Low Molecular Weight Heparin
  •  Anti Xa
  • Anti Factor Xa
​Additional Comments
  • ​The level of low molecular weight Heparin is dependent on the Heparin administered, the dose, the frequency of the dose, the time the specimen was drawn relative to the dose, the weight of the patient and both the liver function and renal function of the patient.
  • Low Molecular Weight Heparin cannot be used interchangeably (unit for unit) with unfractionated heparin or other low molecular weight heparin as they differ in their manufacturing process, molecular weight distribution, anti-Xa and anti-11a activities and dosage
SHR LIS Test Code​
  • ​XAHEP (For Laboratory Use Only)


​If you choose to print this information, it is valid only on date of print.

Laboratory Controlled Document LSM-267 v3

Last Modified: Friday, May 28, 2021 |
Questions or feedback about this page?