Name: Prothrombin Time/INR
Test Name: Prothrombin Time/INR
Health Link Test Code: PT
LIS Test Code: PROX
CPT Code(s): 85610
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.
Collection Container: Light blue top (3.2% NaCitrate)
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
24 hours if unspun; 4 hours if spun and opened
2 weeks at -20°C; 6 months at -70°C
Sample Analyzed: Plasma
Testing Volume: 0.5 mL
Pediatric Testing Volume: 0.5 mL
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.
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.
Grossly hemolyzed specimens, clotted specimens, partially filled tubes and specimens greater than 24 hours old when received by the laboratory are not acceptable.
|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
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.
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.