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International Normalised Ratio – INR

Category Haematology
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 & container required 4.5 mL sodium citrate (pale blue top) adults1.8 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.