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HelpTest Code UFH Unfractionated Heparin Anti-Xa Assay
Specimen Requirements
Submit only one of the following specimens
Specimen Type: Whole Blood
Container/Tube: 2 Light Blue Top (3.2% Sodium Citrate)
Volume: 2 × 2.7 mL Whole Blood (Tubes must be full)
Collection Instructions: Send whole blood specimens to laboratory immediately.
Specimen Type: Platelet Poor Plasma
Container/Tube: 2 Light Blue Top (3.2% Sodium Citrate)
Submission Container/Tube: Plastic Vial
Minimum Volume: 1.0 mL plasma
Collection Instructions:
1. Light blue top tube must be properly filled with whole blood.
2. Whole blood specimen should be double centrifuged and plasma separated from cells within 1 hr of collection.
3. Plasma should be separated into 2 aliquots with minimum volume of 1.0 mL each.
4. Freeze the aliquots in well-closed plastic tubes immediately.
Specimen Stability
| Specimen Type | Plasma |
|---|---|
| Ambient | 4 hours |
| Refrigerate | 4 hours |
| Frozen | 14 days (preferred) |
Specimen Condition
| Haemolysis | Gross reject |
|---|---|
| Icterus | Gross reject |
| Lipaemia | Gross reject |
| Others | Clotted or insufficient reject |
Methodology
Chromogenic Assay
Days and Times Performed
Monday through Friday, TAT 7 days
Reference Interval
| Heparin (80 units/kg bolus, then 18 units/kg/h) | 0.30 – 0.70 IU/mL |
|---|
Testing Laboratory
National University Hospital
Haematology, 67725320
Useful For
Monitoring of unfractionated heparin therapy
Service Code
12434
Update
Last updated 11/06/2026
Alias
UFH
Anti-Xa
Laboratory Code
LAB1754