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Lab Dept:
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Coagulation
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Test Name:
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FACTOR XI ASSAY
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General Information
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Lab Order Codes:
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F11
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Synonyms:
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PTA; Antihemophilia Factor C; Hemophilia C; Plasma Thromboplastin Antecedent; Factor XI Activity; Factor 11
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CPT Codes:
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85270 - Clotting factor XI (PTA)
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Test Includes:
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Factor 11 level reported as a %.
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Logistics
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Test Indications:
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Useful for the detection of a single factor congenital homozygous or heterozygous deficiency.
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Lab Testing Sections:
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Coagulation
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Phone Numbers:
Minneapolis:
Saint Paul:
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612-813-6280
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651-220-6550
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Test Availability:
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Daily, 24 hours
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Turnaround Time:
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4 hours
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Special Instructions:
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Patient should not be receiving heparin. If so, this should be noted on the request form. Heparin therapy can affect certain coagulation factors or assays, preclude their performance, or cause spurious results. Indicate when specimen is drawn from a line or a heparin lock. Deliver immediately to the laboratory.
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Specimen
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Specimen Type:
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Whole blood
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Container:
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Light Blue top (Buffered Na Citrate 3.2%) tube
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Draw Volume:
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2.7 mL blood
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Processed Volume:
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0.9 mL plasma
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Collection:
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Patients with hematocrit levels of >55% must have a special tube made to adjust for the hematocrit. Contact the laboratory for special tube.
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Special Processing:
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Lab Staff: Centrifuge specimen, remove plasma aliquot. Run specimen or freeze to store.
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Patient Preparation:
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Avoid heparin therapy for two days prior to the test.
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Sample Rejection:
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Improper tube, Clotted samples, Underfilled tubes, Overfilled tubes, Mislabeled or unlabeled specimens
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Interpretive
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Reference Range:
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Age
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Range
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0 – 1 days:
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24 – 52%
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2 – 5 days:
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39 – 71%
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6 – 30 days:
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40 – 66%
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31 – 90 days:
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55 – 83%
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91 – 180 days:
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62 – 110%
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6 months – 5 years:
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50 – 150%
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6 – 10 years:
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52 – 120%
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11 – 16 years:
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50 – 100%
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>16 years:
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67 – 127%
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Critical Values:
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N/A
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Limitations:
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Interpretation of the results may be limited if patient is receiving anticoagulant therapy or if test is done more then 2 hours after collection.
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Methodology:
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Thromboplastin clotting time correction of Factor 11 deficient plasma. Patient dilutions are compared to a known set of standard dilutions and a percentage is determined.
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Contraindications:
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Patient on anticoagulant therapy.
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References:
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Harmening DH (1997) Clinical Hematology and Fundamentals of Hemostasis
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Andrew M et al (1987) Development of the Human Coagulation System in the Healthy Full-Term Infant, Blood 70:165-72
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Andrew M et al (1988) Development of the Human Coagulation System in the Healthy Premature Infant, Blood 72:1651-57
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Andrew M et al (1992) Development of the Human Coagulation System During Childhood, Blood 80:1998-2005
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Updates:
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5/24/2010: Tubing of patient specimens is no longer prohibited.
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