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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

Platelet poor Coag Citrate Specimen processing:
1. Gently invert tube 2-3 times prior to placing in Centrifuge
2. Centrifuge Citrate whole blood at 4500 rpm for 10 minutes
3. Carefully pipette plasma, avoiding the platelet/buffy coat into a plastic vial
4. Centrifuge plasma at 4500 rpm for 10 minutes
5. Pipette the plasma to a plastic vial, leaving the bottom 0.25 mL undisturbed
6. Outside locations freeze plasma immediately and transport frozen. Samples processed inhouse, if technician can run immediately, you do not need to freeze, if not freeze immediately.
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.
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