Lab Test

Protime INR

PT, Prothrombin Time, Pro-Time, Protime (Prothrombin Time)

Test Codes



Specimens with hematocrit values greater than 55% must have anticoagulant adjusted. Specimens must be re-collected using a specified whole blood to sodium citrate ratio. Contact the performing Laboratory for specific instructions.

Specimen Collection Criteria

Collect: One Light Blue-top Becton-Dickinson 3.2% Sodium Citrate tube.

Physician Office/Draw Specimen Preparation

For optimal results, maintain whole blood specimen at room temperature (20-26°C or 68-78.8°F) prior to transport. Transport to the Laboratory within 24 hours of collection.

Preparation for Courier Transport

Transport: Whole blood at room temperature (20-26°C or 68-78.8°F).

Rejection Criteria

  • Glass tubes and 3.8% Sodium Citrate tubes.
  • Specimens that are clotted or grossly hemolyzed.
  • Inappropriate specimen volume.
  • Thawed or partially thawed specimens.

In-Lab Processing

Maintain specimens at room temperature (20-26°C or 68-78.8°F) prior to testing.


Specimen Stability for Testing:

Whole Blood
Room Temperature (20-26°C or 68-78.8°F): 24 hours
Refrigerated (2-8°C or 36-46°F): Unacceptable
Frozen (-20°C/-4°F or below): Unacceptable

Plasma Aliquot
Room Temperature (20-26°C or 68-78.8°F): Unacceptable
Refrigerated (2-8°C or 36-46°F): Unacceptable
Frozen (-20°C/-4°F or below): 30 days

Specimen Storage in Department Prior to Disposal:

Refrigerated (2-8°C or 36-46°F): 7 days


Farmington Hills Hematology/Coagulation Laboratory
Grosse Pointe Hematology/Coagulation Laboratory
Royal Oak Coagulation Laboratory
Troy Hematology/Coagulation Laboratory


Sunday – Saturday, 24 hours a day.
STAT results available within 30 minutes of receipt in the Laboratory unless further verification is necessary.
Routine results available within 2 hours of receipt in the Laboratory.

Reference Range

PT: 9.2 – 13.5 seconds.

Test Methodology

Photo-Optical Clot Detection (IL ACL-TOP Series)


Oral Anticoagulant Therapeutic Ranges
 INR  Clinical Condition
 2.0 - 3.0   Venous thrombosis, pulmonary embolus.
 2.5 - 3.5   Certain mechanical valves*

  • Prothrombin times are elevated in oral anticoagulant therapy, liver disease, some lupus like inhibitors, congenital deficiency of factor II, V, VII, or X.
  • Oral anticoagulants affect protime values.

Clinical Utility

This assay aids in the evaluation of the extrinsic coagulation system, aids in the screening for congenital deficiencies of factors II, V, VII, and X, dysfibrinogenemia, afibrinogenemia, Coumadin or warfarin effect, liver failure, disseminated intravascular coagulation and in screening for vitamin K deficiency.

CPT Codes



Last Updated


Microtainer® and Vacutainer® are registered trademarks of Becton, Dickinson and Company.
UroVysion® is a registered trademark of Abbott Laboratories. ThinPrep® is a registered trademark of Hologic, Incorporated.


This directory currently reflects information only for specimens collected and/or processed at the
Farmington Hills, Grosse Pointe, Royal Oak, and Troy campuses.