Factor XI Activity
Also known as: Antihemophilic Factor C, Plasma Thromboplastin Antecedent (PTA)
Use
Evaluate isolated aPTT prolongation and to document specific factor deficiency6-8
Special Instructions
If the patient's hematocrit exceeds 55%, the volume of citrate in the collection tube must be adjusted. Refer to Coagulation Collection Procedures for directions. Ideally, the patient should not be on anticoagulant therapy. Avoid warfarin therapy for two weeks prior to the test and heparin, direct Xa, and thrombin inhibitor therapies for about three days prior to testing.
Limitations
Direct Xa or thrombin inhibitor therapy may cause factitiously low results. Acquired inhibitors of factor XI are very rare, but spontaneous autoantibodies can occur in patients with underlying autoimmune disorders or in patients treated with chlorpromazine. The bleeding severity does not always correlate with Factor XI plasma levels.
Methodology
Other
Biomarkers
LOINC Codes
- 3226-8
Result Turnaround Time
2-3 days
Related Documents
For more information, please review the documents below
Specimen
Plasma
Volume
1 mL
Minimum Volume
Not provided
Container
Blue-top (sodium citrate) tube
Collection Instructions
Blood should be collected in a blue-top tube containing 3.2% buffered sodium citrate. Evacuated collection tubes must be filled to completion to ensure a proper blood-to-anticoagulant ratio. Mix immediately by gentle inversion at least six times. A discard tube is not required unless using a winged collection set.
Patient Preparation
Ideally, the patient should not be on anticoagulant therapy. Avoid warfarin therapy for two weeks prior to the test and heparin, direct Xa, and thrombin inhibitor therapies for about three days prior to testing.
Storage Instructions
Freeze.
Causes for Rejection
Severe hemolysis; improper labeling; clotted specimen; specimen diluted with IV fluids; samples thawed in transit; improper sample type; sample out of stability
Stability Requirements
| Temperature | Period |
|---|---|
| Frozen | 28 days |
Other tests from different labs that may be relevant