| Test Name: |
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Activated Protein C Resistance
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| Test Code(s): |
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APC-R / XAPCR
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| CPT Code(s): |
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85307
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| Test Description: |
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Test Component: Ratio of two APTT-based assays, one with activated protein C added.
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| Methodology: |
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Mechanical Clot Detection
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| Clinical Significance: |
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Screening test used as a predictor of the Factor V Leiden gene mutation, factor V:Q506 mutation.
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| Days Performed: |
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Mon-Fri, dayshift - day varies.
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| Turnaround Time: |
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Stat: Not available stat.
Routine: 7 - 10 working days.
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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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Indicate if patient is receiving anticoagulant (warfarin/Heparin/Vitamin K antagonist), direct thrombin inhibitor or fibrinolytic agent therapy and duration. Do NOT draw through a line containing heparin. The venipuncture MUST be atraumatic to avoid hemolysis and contamination with tissue factors and platelets. Tube must be allowed to fill completely.
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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: Two full 3.5 mL tubes
Pediatrics: Pediatric tube filled to fill mark
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| Sample Analyzed: |
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Plasma
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| Volume Required: |
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Preferred: 1 mL
Pediatrics: 0.5 mL
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| Specimen Processing: |
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KEEP ONE TUBE UNOPENED AND UNSPUN at room temperature. Centrifuge the other tube to obtain platelet poor plasma (platelet count should be less than 10 K/µL). Separate plasma from cells and transfer to plastic vial. Freeze plasma at -20°C or below.
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| Specimen Transport: |
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Transport unopened tubes at room temperature to UWHC Core Laboratory (B4/220) within 4 hours of collection. Otherwise, transport one unopened tube at room temperature and a frozen plasma aliquot on dry ice.
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| Unacceptable Criteria: |
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Hemolyzed or clotted specimens are not acceptable. A partially filled tube is not acceptable. Activated Protein C Resistance cannot be done on patients with a Lupus Anticoagulant. Alternatively, Factor V Leiden Gene Mutation is available.
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| Stability: |
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Ambient: 4 hours on spun tube
Refrigerated: Not acceptable
Frozen: Plasma:2 weeks at -20°C; 6 months at -70°C. Whole Blood: Not acceptable
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Interpretation
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Reference Interval:
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Age 12 months and up: Ratio greater than or equal to 2.1 is negative for APC resistance.
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| Test Limitations: |
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This method uses Factor V deficient plasma; therefore, APC resistance due to a mutation other than a Factor V Leiden will not be detected. Extreme Factor V activity deficiency and a presence of lupus anticoagulant may cause an erroneous result.
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| Additional Information: |
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This is NOT the assay for Protein C Activity or C Reactive Protein.
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