Laboratory Services

Prothrombin Time with INR

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Updated Test Information:

Test Description
Prothrombin Time with INR
Synonym(s)

PT, INR, Protime

Test ID
PT
General Information

The Prothrombin Time test measures, as a whole, the activity of the coagulation factor II (prothrombin). Is used in the monitoring of coagulation therapy and vitamin K antagonist therapy


Interferences: Our prothrombin time test is insensitive to unfractionated heparin levels up to 1 IU/mL and to low molecular weight heparin levels up to 1.5 anti-Xa IU/mL. Thrombin inhibitors present in the sample to be tested may lead to a prolonged prothrombin time. Vitamin K antagonists will depress plasma levels of factors II (prothrombin), VII (proconvertin), X (Stuart factor) and IX (antihemophilic factor B)

Specimen Type

Plasma

Specimen Requirements

Light Blue
Aliquot Tube

Specimen Collection / Processing Instructions

Light Blue - Centrifuge immediately, transfer plasma to aliquot tube and freeze at less than -20°C.

Minimum Sample Volume

The sodium citrate collection tube must be filled to 90% of capacity.

Pediatric Min. Volume (if applicable)

The sodium citrate collection tube must be filled to 90% of capacity.

Additional Processing Details

If specimen will be received >24 hours after collection, centrifuge for 15 minutes at 2000-2500g. Transfer the plasma to an aliquot tube and store frozen at ≤ -20°C. DO NOT store plasma at 2° - 8°C

Stability

Plasma Na Citrate
  - Frozen (preferred): 14 days
  - Room Temperature: 24 hours
  - Refrigerated: Unacceptable


Unspun Whole Blood in Na Citrate
 -Room temperature: 24 hours
 -Refrigerated: Unacceptable
 -Frozen: Unacceptable

Unacceptable Specimen Conditions

Refrigerated specimens; Quantity not sufficent; improperly labeled specimens; specimens not collected in 3.2% buffered sodium citrate tube; clotted specimens; under or over filled specimen tubes; severe hemolysis; improperly labeled specimens

Methodology

Automated

Estimated TAT

0-2 days

Testing Schedule

Monday-Saturday, & STAT

CPT Code(s)

85610

Reference Range

11.8-14.7 seconds


Standard intensity warfarin therapeutic range: 2.0 – 3.0 INR


High intensity warfarin therapeutic range: 2.5 – 3.5 INR

Reflex Conditions

None

Performing Lab

Incyte Diagnostics

LOINC Code(s)

6301-6