Imperial Collage Healthcare

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International Normalised Ratio – INR

Test Background
INR is derived from the PT; it is used to monitor warfarin dosage and will only be reported where a patient is taking warfarin or other dicoumarol drug.

Clinical Indications
For the monitoring of vitamin K antagonist therapy (warfarin, phenindione, etc.)

Reference Range
Therapeutic range dependent on clinical requirement for anticoagulation.

Sample Required
4.5 mL sodium citrate (pale blue top) adults 1.8 mL sodium citrate (pale blue top) paediatrics

Turnaround Time
4 hours

Special handling: avoid prolonged stasis during venepuncture. Sample must be received by lab within 4 hours of collection. Please note: samples will be rejected if underfilled or overfilled.

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