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Test Code F11HM Factor (11) XI for Hemophilia Monitoring

Specimen and Container/Tube

Specimen Type: Plasma

Preferred Specimen: Light Blue Top Tube, 3.2% Sodium Citrate

Other Acceptable specimens: N/A

Specimen Handling and Transport Instructions

UCMC Onsite Instructions: 

Collect specimen per standard collection procedure and send to laboratory immediately. 

 

NOTE: Once each blue top tube is completely filled, gently invert the sample tube at least five times to ensure complete mixing of the contents.

 

UCMC Offsite and UC MedLab Outreach Instructions: 

  • Collect specimen per standard collection procedure.
  • Once each blue top tube is completely filled, gently invert the sample tube at least five times to ensure complete mixing of the contents.
  • Centrifuge specimens at >2500 x g for 10 minutes at room temperature.
  • Carefully remove plasma from cells using a plastic transfer pipette avoiding buffy coat.
  • Aliquot removed plasma into 2 plastic tubes containing a minimum of 1.0 mL of specimen in each tube.
  • Plasma samples must then be frozen at -20oC.
  • Once solidly frozen, they must be shipped on dry ice. Samples that have thawed in transit will be rejected.

Rejection Criteria

  • Common specimen rejected situations include: incorrect specimen type, insufficient volume, missing or incomplete specimen identifiers, incorrect specimen transport, or specimens outside stability limits. 
  • Specimens that have wrong ratio of blood to anticoagulant (fill volume), clotted or grossly hemolyzed.

Reference Values

 

Test

Age

Sex

Reference Range

Factor XI Activity

All

All

70 - 144%

Factor XI Inhibitor

All

All

<0.6 Bethesda Units

Critical Values

Analyte

Unit

Low

High

Age

N/A

N/A

N/A

N/A

N/A

CPT Codes

85270, 85335

LOINC Codes

3226-8, 3224-3

Volume

Preferred Volume: 2.0 mL

 

Minimum Volume: 1.5 mL

Specimen Stability

Storage Temperature

Stability

Room temperature

4 hours

Refrigerated

not acceptable

Frozen

30 days

Collection Instructions

Collect specimen per standard laboratory collection procedures. 

 

NOTE: Once each blue top tube is completely filled, gently invert the sample tube at least five times to ensure complete mixing of the contents.

Turnaround Time

Turnaround times are relative to the time the specimen is received in the test laboratory. 

STAT Turnaround Time: N/A

 

Routine Turnaround Time: Up to 3 days

 

Testing Schedule: Monday to Friday, 8 am to 3:30 pm

 

 

Please consult Lab medicine resident on-call (pager 7910) if more rapid test performance is deemed necessary.

Clinical Indications

Diagnosing deficiency of coagulation factor XI.

 

Investigation of prolonged aPTT.

 

Bethesda assay for Factor XI inhibitor titers is generally performed in the setting of significantly decreased levels of Factor XI.

Methodology

Clotting

Synonyms/Keyword Search

Factor XI, Factor 11 Activity, F11, Fa11,

Factor 11 inhibitor titer, Hemophilia C

Additional Information

3.2% sodium citrate light blue top tubes must have 9 to 1 ratio of blood to anticoagulant.

Last Review Date

03/13/2024

Test Components

  • Factor XI activity
  • Factor XI inhibitor titer
  • Pathology interpretation