Prothrombin Time

PT, PTINR, INR
Core Laboratory & Transfusion Medicine
Hematology
Blood
PTINR

MSH Coagulation requisition form (MS 520)
The prothrombin time (PT) is the screening test for the reactions of the extrinsic pathway. PT is most commonly used for monitoring oral anticoagulant therapy and for performing factor assays for the extrinsic system.
A prolonged PT value is most often indicative of a decreased level of one or more of the factors in the extrinsic or common pathways of coagulation. An increased PT usually indicates defective or decreased synthesis of vitamin K-dependent clotting factors. The PT assay is also sensitive to decreases in factor V and fibrinogen, which may accompany end-stage liver disease or, disseminated intravascular coagulation (DIC).
Plasma (3.2% Na Citrate)
Full draw
Light Blue citrate tube
Collection Containers – Tube Types
Adult: 2.7 mL
Pediatric Micro tube: 1 mL
Send whole blood sample(s) at room temperature as soon as possible.
If specimens cannot be shipped immediately, centrifuge and separate plasma within 1 hour of collection, send frozen plasma on dry ice
Fridge: N/A
Room Temperature: 24 hours Freezer: - 20 °C 2 weeks - 70 °C 6 months
Automated Coagulation Analyzer
24 hours, 7 days/week.
1 hour
2 hours
Adult: PT: 9.7-11.8 sec, INR: 0.9-1.1
Full-term Infant at Birth: PT: 10.1 – 15.9 sec, INR: 0.53 – 1.62
Premature Infant of 30 to 36 Weeks gestational age: PT: 10.6 – 16.2 sec, INR: 0.61 – 1.70
Premature Infant of < 28 weeks gestational age: PT: 12.9-28.5 sec In case of discrepancies, always interpret results using reference ranges as stated on laboratory reports and/or electronic patient chart.
416-586-4800 Extension 4688
Must indicate anticoagulant status