UW Hospital and Clinics Lab Test Directory
| Test Name: |
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Prothrombin Time/INR
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| Test Code(s): |
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PROX / PT
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| CPT Code(s): |
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85610
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| Methodology: |
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Mechanical Clot Detection
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| Days Performed: |
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Daily, 24 hours.
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| Turnaround Time: |
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Stat: 1 hour.
Routine: 4 hours.
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Specimen Requirements
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| Specimen: |
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Blood
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| Collection Instructions: |
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The venipuncture MUST be atraumatic to avoid hemolysis and contamination with tissue factors and platelets. Tube MUST be allowed to fill up to "fill" line indicated on tube.
If unable to collect 1.8 ml tube (pediatrics only) please call Core Coagulation Lab at 263-9617 or Special Coagulation Lab at 263-5005 for alternate tube and instructions.
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| Collection Container: |
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Preferred: Light blue top (3.2% NaCitrate)
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| Collection Volume: |
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Preferred: 3.5 mL
Pediatrics: 1.8 mL
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| Sample Analyzed: |
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Plasma
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| Volume Required: |
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Preferred: 0.5 mL
Pediatrics: 0.5 mL
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| Specimen Processing: |
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Centrifuge specimen to yield platelet poor plasma (platelet count should be less than 10K/uL). Separate plasma and transfer to plastic tube or vial. Freeze plasma at -20°C or below.
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| Specimen Transport: |
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Transport whole blood specimen on an unopened tube at room temperature to the laboratory within 24 hours of collection. Specimens that have been opened and spun must be less than 4 hours old when received by the laboratory. Otherwise, transport frozen plasma aliquot on dry ice.
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| Unacceptable Criteria: |
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Grossly hemolyzed specimens, clotted specimens, partially filled tubes and specimens greater than 24 hours old when received by the laboratory are not acceptable.
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| Stability: |
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Ambient: 24 hours if unspun; 4 hours if spun and opened
Refrigerated: Not acceptable
Frozen: 2 weeks at -20°C; 6 months at -70°C
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Interpretation
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Reference Interval:
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| 0 days - 6 months: |
0.8-1.2 |
| 7 months and up: |
0.9-1.1 |
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| Critical Calls: |
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View
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| Additional Information: |
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INR is the International Normalized Ratio which takes into account the instrumentation and reagent system used at UWHC. The INR is intended to standardize reporting of the prothrombin time. For patients NOT on anticoagulants, the reference range for the INR is 0.9 -1.1. The recommended therapeutic range for oral anticoagulant therapy is INR of 2.0-3.0. (Exception: The recommended range for many mechanical valves is INR 2.5-3.5.) Reference: CHEST, Vol 126, No.3, September 2004, page 470s.
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PT Protime International Normalized Ratio INR
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