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Test Code FXI Factor XI Assay

Laboratory Code

LAB309

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 Not available
Frozen 14 days (preferred)

Panel Information

Panel includes the following tests:

Methodology

Activated Partial Thromboplastin Clot-Based Assay

Days and Times Performed

Tuesday through Friday, TAT 7 days

Specimen Condition

Haemolysis Gross reject
Icterus Gross reject
Lipaemia Gross reject
Others Clotted or insufficient reject

Reference Interval

74 – 126 %

Testing Laboratory

National University Hospital
Haematology, 67725320

Service Code

12503

LOINC Code Information

APTT 14979-9
FACTOR XI 3226-8
APPT (1+1) CORRECTION 5946-9
CONTROL PLASMA 13488-2

 

Alias

Factor XI Activity

Update

Last updated 14/01/2026

Reflex Tests

  • APTT mixing study if APTT is > 37.0 seconds