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Lab Dept:
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Coagulation
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Test Name:
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INR (FAIRVIEW UNIVERSITY)
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General Information
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Lab Order Codes:
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PTU
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Synonyms:
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Protime to U of M; Prothrombin Time to U of M; PT to U of M; International Normalized Ratio; INR
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CPT Codes:
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85610 - Prothrombin time
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Test Includes:
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INR; Protime (PT) is Not reported
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Logistics
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Test Indications:
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Useful for evaluating the extrinsic and common pathways of the coagulation system; aid in screening for congenital deficiencies of factors II, V, VII, and X, dysfibrinogenemia, afibrinogenemia, coumarin effect, liver disease, disseminated intravascular coagulation (DIC), and vitamin K deficiency.
The International Normalized Ratio (INR) is now the most widely recommended test for monitoring oral anticoagulation because the INR, unlike the prothrombin time (PT) reported in seconds, is largely independent of the specific instrument and reagent used.
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Lab Testing Section:
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Coagulation - Sendouts
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Referred to:
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Fairview University Medical Center
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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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8 hours routine
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Special Instructions:
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Patient should not be receiving Coumadin® or heparin. If so, this should be noted on the request form. Heparin or warfarin 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 in a 3 mL tube (Minimum: 2.7 mL in a 3 mL tube)
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Processed Volume:
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Specimen will be processed by reference lab facility.
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Collection:
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Patients with hematocrit levels >55% must have a special tube made to adjust for the hematocrit, contact laboratory for special tube.
Fill tube completely. Mix thoroughly by gentle inversion.
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Special Processing:
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Lab Staff: Do Not centrifuge. Send to reference lab in original Vacutainer®. Specimen must arrive within 24 hours. If more than 24 hours is required for transport, contact laboratory for processing instructions.
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Patient Preparation:
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None
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Sample Rejection:
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Improper tube, Clotted specimen, 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 month:
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0.81 – 1.30
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1 – 6 months:
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0.81 – 1.17
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> 6 months:
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0.86 – 1.14
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Critical Values:
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>5.5
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Limitations:
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Increased in patients taking oral contraceptives
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Methodology:
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Quick One Stage Prothrombin Time
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References:
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Fairview University Medical Center Laboratory Web Page June/2004 http://labguide.fairview.org/diagnostic.asp
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Harmening DH (1997) Clinical Hematology and Fundamentals of Hemostasis
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Updates:
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6/3/2004: Reference ranges changed from one range of >1 year: 0.85 – 1.15 to the expanded ranges by age listed under Reference Range:
Draw volume was updated from 4.5 mL to 2.7 mL blood.
5/25/2010: Tubing patient specimens is no longer prohibited.
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