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Prothrombin Time/INR

Source Blood
Mnemonic PT
Specimen Requirements

Adult:
1 x 2.7 mL blue top sodium citrate plastic tube is preferred. 4.5 mL blue top sodium citrate glass tube is also acceptable.

Pediatric:
1 x 2.7 or 1.8 mL short-draw blue top sodium citrate tube

Whole blood. VENOUS COLLECTION ONLY. Skin puncture (capillary) collection is not acceptable.

It is important to fill tube to maximum draw.
Mix well by inverting. Indicate collection time on tube.

When using a winged blood collection set (butterfly needle) a discard tube must be used to remove the air in the tubing,if only a citrate tube is drawn or is the first tube drawn.


Adjusted PT:
For patients with high hematocrit results, an adjusted citrate tube may be required for collection; the amount of anticoagulant in the tube has been modified to be specific for the patient.
CLS collection of adjusted PT:
- If 'adjusted PT' is indicated, hematology may provide an adjusted citrate tube or request a CBC and PT collection. An EDTA sample is required to calculate the anticoagulant ratio. If CBC is not requested, order and collect an extra EDTA tube.
- An adjusted citrate tube may be provided for recollection of the PT after the CBC is completed.
- The adjusted citrate tube will be clearly marked with a 'fill line'; the tube must be filled to that line to maintain the correct anticoagulant/sample ratio.
- The adjusted tube does not have a vacuum and must be collected using a syringe. Remove cap from PT tube, remove needle from syringe and slowly dispense blood down the inside of the tube, filling to the indicated fill line.
- Keep collected tubes together with an elastic band and place in a separate bag labelled "Adjusted PT". Deliver directly to Hematology.

Specimen Handling DO NOT centrifuge until tube arrives at testing site. Keep at room temperature.
MUST be tested within 24 hours of collection.
Additional Information Prothrombin Time is reported in INR (International Normalized Ratio)
Testing Location Hematology-All Sites
Rural: CRL
Testing Frequency Daily
Alternate Name(s) PT, INR
Reference Interval

INR: 0.9 - 1.1                  Click here for critical values.

INR Therapeutic Ranges:

 Condition  INR
 Prevention of Deep Vein Thrombosis  2.0 - 3.0 
 Prevention Recurrent Thrombosis  2.0 - 3.0 
 Cardiac Valve Replacement:
        
Tissue Valve
        
 Mechanical Valve 
 
 2.0 - 3.0
 2.5 - 3.5
 Recurrent Systemic Embolism  2.5-3.5