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Jun 20, 2016

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UWHC,UWMF,

Clinical Hub,Tools & Resources,UWHC Lab Test Directory,Coagulation

Prothrombin Time/INR

Prothrombin Time/INR (PT) Coagulation Lab Test

Name: Prothrombin Time/INR

Test Name: Prothrombin Time/INR

Health Link Test Code: PT

LIS Test Code: PROX

CPT Code(s): 85610

Clinical Information:

Methodology

University Hospital- Optical clot detection

The American Center, East Clinic, West Clinic, Digestive Health Clinic- Mechanical Clot detection

Days Performed: Daily, 24 hours.

In-Lab Turnaround Time: 4 hours.

Stat In-Lab Turnaround Time: 1 hour.

Specimen: Blood

Collection Container: Light blue top (3.2% NaCitrate)

Collection Instructions:

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 UWHC Coagulation Lab at (608)263-9617 or UWHC Special Coagulation Lab at (608) 263-5005 for alternate tube and instructions.

Collection Volume: 3.5 mL

Pediatric Collection Volume: 1.8 mL

Stability Ambient:

24 hours if unspun; 4 hours if spun and opened

Stability Refridgerated:

Not acceptable

Stability Frozen:

2 weeks at -20°C; 6 months at -70°C

Sample Analyzed: Plasma

Testing Volume: 0.5 mL

Pediatric Testing Volume: 0.5 mL

Specimen Processing:

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.

Specimen Transport:

Transport whole blood specimen in 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.

Unacceptable Criteria:

Grossly hemolyzed specimens, clotted specimens, partially filled tubes and specimens greater than 24 hours old when received by the laboratory are not acceptable.

Interpretation:

  University Hospital The American Center, East Clinic, West Clinic, DHC 
 7 months and up:  0.9 - 1.2 0.9 - 1.1

 

 

 

Interpretation Type: Reference Interval

Critical Calls: yes

Additional Information:

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 0.9-1.2. The recommended therapeutic range for warfarin is an INR of 2.0-3.0. (Exception: The recommended range for many mechanical valves is INR 2.5-3.5.) Reference: CHEST 2012; 141 pgs e5925-e5945.

 

University Hospital

Heparin concentrations exceeding 1.2 IU/mL may prolong the INR and thus interfere with monitoring of vitamin K antagonists such as warfarin. Inhibitors of the Lupus type anticoagulants can influence prothrombin and lead to INR’s that do not accurately reflect the true level of anticoagulation. Direct thrombin inhibitors in therapeutic dose result in prolonged prothrombin times.

 

The American Center, East Clinic, West Clinic, Digestive Health Clinic

Heparin concentrations exceeding 1.0 IU/mL  and LMWH concentrations exceeding 1.5 anti-Xa IU/mL may prolong the INR and thus interfere with monitoring of vitamin K antagonists such as warfarin. Inhibitors of the Lupus type anticoagulants can influence prothrombin and lead to INR’s that do not accurately reflect the true level of anticoagulation. Direct thrombin inhibitors in therapeutic dose result in prolonged prothrombin times.