Factor XI Activity
| Factor XI Activity | | | |
| Number | | 086314 |
| CPT | | 85270 |
| Related Information | | Hemostasis and Thrombosis Appendix |
| Synonyms | | Antihemophilic Factor C ; Plasma Thromboplastin Antecedent (PTA) |
| 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. |
| Specimen | | Plasma, frozen |
| Volume | | 2 mL |
| Minimum Volume | | 1 mL |
| Container | | Blue-top (sodium citrate) tube |
Collection | | Blood should be collected in a blue-top tube containing
3.2% buffered sodium citrate.1 Evacuated
collection tubes must be filled to completion to ensure a
proper blood to anticoagulant ratio.2,3 The
sample should be mixed immediately by gentle inversion at
least six times to ensure adequate mixing of the
anticoagulant with the blood. A discard tube is not
required prior to collection of coagulation
samples.4,5 When noncitrate tubes are collected
for other tests, collect sterile and nonadditive (red top)
tubes prior to citrate (blue top) tubes. Any tube
containing an alternate anticoagulant should be collected
after the blue-top tube. Gel-barrier tubes and serum tubes
with clot initiators should also be collected after the
citrate tubes. Centrifuge and carefully remove the plasma
using a plastic transfer pipette, being careful not to
disturb the cells. Transfer the plasma into a LabCorp PP
transpak frozen purple tube with screw cap (LabCorp
No 49482). Freeze immediately and maintain
frozen until tested. To avoid delays in turnaround time
when requesting multiple tests on frozen samples, please
submit separate frozen specimens for each test requested.
Please print and use the Specimen
Collection Bulletin as a tube-filling guide. |
| Storage Instructions | | Freeze |
| Patient Preparation | | Avoid warfarin (Coumadin®) therapy for 2 weeks and heparin therapy for 2 days prior to the test. Do not draw from an arm with a heparin lock or heparinized catheter. |
| Causes for Rejection | | Gross hemolysis; clotted specimen; frozen specimen thawed in transit; improper labeling |
| Reference Interval | | Adults: 60% to 135%. In newborns, levels are lower but gradually reach adult ranges by 6 months of age.6 |
| Use | | Document specific factor deficiency7,8,9 |
| Methodology | | Factor XI activity is determined utilizing an aPTT-based one-stage clotting time assay. Factor XI-depleted plasma is used as the substrate, and the clotting time with the patient plasma is compared to the clotting time of normal pooled plasma. |
| Additional Information | | Factor XI is a 160 kilodalton glycoprotein proenzyme that is produced by the liver and megakaryocytes.7,8,9 Factor XI's plasma concentration is 4-6 mg/mL and half-life is about 60 hours.7 Hereditary factor XI deficiency, referred to as hemophilia C, is transmitted as an autosomal recessive mutation.7,8,9 This condition affects both males and females and the majority of reported cases have been diagnosed in Ashkenazi Jews.7,8 As many as 11% of Ashkenazi Jews will be heterozygous for factor XI deficiency and up to 0.3% will be homozygous.9 Individuals who are heterozygous for factor XI deficiency mutation typically have levels between 30% to 60% and homozygotes have levels <20%.9 The bleeding associated with factor XI deficiency is generally not as severe as that found with hemophilia A or B.8 Severity of bleeding does not always correlate with the plasma level of factor XI.7,8 Individuals with factor XI deficiency can suffer from easy bruising, epistaxis, hematuria, and menorrhagia.7,8 Excessive bleeding postpartum and after oral cavity surgery can occur.8 Acquired inhibitors of factor XI are very rare.7 Spontaneous autoantibodies are more common and generally occur in patients with underlying autoimmune disorders or in patients treated with chlorpromazine.7 |
| Footnotes | | - Adcock DM, Kressin DC, and Marlar RA, “Effect of 3.2% vs 3.8% Sodium Citrate Concentration on Routine Coagulation Testing,” Am J Clin Pathol, 1997, 107(1):105-10.
- Reneke J, Etzell J, Leslie S, et al, “Prolonged Prothrombin Time and Activated Partial Thromboplastin Time Due to Underfilled Specimen Tubes With 109 mmol/L (3.2%) Citrate Anticoagulant,” Am J Clin Pathol, 1998, 109(6):754-7.
- “National Committee for Clinical Laboratory Standardization: Collection, Transport, and Processing of Blood Specimens for Coagulation Testing and General Performance of Coagulation Assays; Approved Guideline,” Third Edition, Villanova: NCCLS Document H21-A3:11(23), 1999.
- Gottfried EL and Adachi MM, “Prothrombin Time and Activated Partial Thromboplastin Time Can Be Performed on the First Tube,” Am J Clin Pathol, 1997, 107(6):681-3.
- McGlasson DL, More L, Best HA, et al, “Drawing Specimens for Coagulation Testing: Is a Second Tube Necessary?” Clin Lab Sci, 1999, 12(3):137-9.
- Van Cott EM and Laposata M, “Coagulation,” Laboratory Test Handbook With Key Word Index, Jacobs DS, DeMott WR, and Oxley DK eds, Hudson, OH: Lexi-Comp, 2001, 327-58.
- Adcock DM, Jensen R, Johns CS, et al, Coagulation Handbook, Esoterix Coagulation, 2002.
- Roberts HR and Escobar MA, “Less Common Congenital Disorders of Hemostasis,” Consultative Hemostasis and Thrombosis, Kitchens CS, Alving BM, and Kessler CM, eds, Philadelphia, PA: WB Saunders Co, 2002, 57-71.
- Triplett DA, “Thrombophilia,” Clinical Laboratory Medicine, 2nd ed, McClatchey KD, ed, Philadelphia, PA: Lippincott Williams and Wilkins, 2002, 1033-49
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