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Prothrombin Time and International Normalized Ratio (PT/INR)


This test is performed on a Sysmex fully automated coagulation system which utilizes optical detection technology.

Test Utility

The test is used to measure and evaluate bleeding or excessive clotting disorders. The INR is an international normalized ratio calculated from the PT and is used to monitor treatment in individuals taking the anticoagulant Warfarin.

Specimen Collection and Preparation

Collect a blood sample in the following tube:

  • Light Blue 3.2% Sodium Citrate Tube – Tube must be filled to 90% of minimum/maximum etched fill line

  • If possible, centrifuge the specimen at 3000 rpm for 15 min, remove plasma and freeze

Specimen Storage and Stability

Store whole blood at the following temperatures:

  • Room temperature: 24 hours

  • Refrigerated 2°C to 8°C:  Unacceptable

  • Frozen: Separated plasma only.

Specimen Rejection

  • Insufficient sample volume – Tube must be filled to with 90% of etched fill line

  • Sample not stored at proper temperature

  • Frozen whole blood

  • Hemolyzed samples

  • Severely lipemic specimens

  • Specimen labeled incorrectly or not labeled

Reference Pages


Monday – Saturday

Result available within 24 hours of receipt in laboratory

NOTE: Specimens are refrigerated (2-8°) for 7 days before disposal

STAT results available within 2 hours of receipt in the laboratory


Vibra Health Laboratory  

1307- A, Allen Dr 

Troy, MI 48083 

(248) 846-0663

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