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Test Code PT Prothrombin Time (PT) and International Normalized Ratio (INR)

Performing Laboratory

Hunterdon Medical Center Laboratory

Useful For

The Prothrombin Time (PT/INR) is used to monitor the effectiveness of oral anticoagulant therapy (warfarin, Coumadin and congeners).

The PT/INR is also a screening tool to detect deficiencies of Factors: I, II, V, VII and X due to: hereditary coagulation disorders, liver disease or Vitamin K deficiency.

Special Instructions

Note: Specimen must be filled to ETCHED line located on the Blue top tube in order to acheive a ratio of 9 parts blood to 1 part anticoagulant.

Specimen Required

Container/Tube: Blue Top (Na Citrate)

Specimen Volume: Must be filled to Etched line located on tube.

Specimen Type

Citrated Plasma

Specimen Transport Temperature

Ambient temperature.

Do not refrigerate.

Specimen Stability

Ambient temperature. Deliver ≤24 hours. 

Perform testing within 24 hours

Do not refrigerate.

Reject Specimen Due To

Tube not properly filled, underfilled or overfilled

Clotted

Hemolysis

Day(s) Test Set up

Monday through Sunday

Available STAT

Reference Values

PT: 9.0 - 13.4 secs

INR: 0.8 – 1.2

 

Suggested values for INR for prophylaxis of venous thrombosis, deep vein thrombosis (DVT), pulmonary embolus (PE), MI, atrial fibrillation, tissue heart valves, valvular heart disease: INR: 2.0-3.0

Suggested INR for mechanical, prosthetic heart valves: INR: 2.5-3.5

Methodology

Turbidimetric

CPT Code

85610

Loinc Code

5902-2

Test Includes

Includes INR (International Normalized Ratio).

Generation of the INR value eliminates problems associated with comparing PT results and allows physicians to accurately monitor oral anticoagulant therapy on a worldwide basis.