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Test Code LAB320 Prothrombin Time (PT)

Additional Codes

PT INR

Includes:

Prothrombin Time (PT) and calculated INR

Collection:

Specimen: Blood 

Container: Blue Top Tube with 3.2% (0.109 M) buffered Sodium Citrate anticoagulant only

Specimen Volume: 3.5 mL Must be filled to arrow (Greiner tube Black Disk) or line (BD)

Pediatric Collection: 2.0 mL Must be filled to arrow (Greiner tube White Disk) or line (BD)

Notes: 

  • Samples not filled properly will be rejected (over or under filled).
  • If the patient's hematocrit is >55%, call Lab Client Services at 792-0707 to obtain an anticoagulant adjusted tube.
  • For collection information and guidance refer to  MUSC Laboratory Services Hemostasis / Coagulation Collection Guidelines .

Stability:

Room Temperature: 24 hours Whole Blood

Refrigerated: Unacceptable

Frozen at or below -20°C: 2 weeks 

Note: Frozen samples must be platelet poor plasma aliquoted from primary tube. Label as Na Citrate or blue top plasma.

Turnaround Time (TAT):

OR/Trauma: 40 minutes

STAT: 1 HOUR

Routine: 3 HOURS

Test Availability:

Daily / 24 Hours / Available STAT

Performing Laboratory Section:

COAGULATION / UMC MAIN LABORATORY

Reference Interval:

PT:

Age Range Normal Range
< 30 Days 10.9 - 13.9 seconds
> 30 days 12.0 - 14.6 seconds

 

INR:

Age Range Normal Range
n/a 0.90 - 1.20

 

Interpretive Data:

In patients on warfarin therapy, the range for therapeutic INR (1.5 - 3.5) will depend on the clinical disorder being treated.