International Normalised Ratio (INR)

Coagulation

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Description

The INR is a widely adopted reporting system for monitoring the vitamin K antagonist oral anticoagulants and which standardizes the variability in thromboplastin reagents/instruments of analysis to the effects of anticoagulant therapy.

The International Normalized Ratio (INR) is derived from the prothrombin time. However, reference ranges for the Prothrombin time can vary between laboratories depending on the sensitivity of the reagent and the technology used to determine the clotting times. The prothrombin ratio is derived from the patient’s prothrombin time and is relative to the expected result in a normal patient. This PT ratio combined with the sensitivity of the reagent employed provides the INR. In theory, the INR obtained in any given patient on anticoagulants should be same anywhere in the world regardless of reagent analyser combination.

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Sample Type

Plasma ( Citrate 2.7ml Blue ) x 1

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Reference Range

Therapeutic ranges exist dependant upon clinical indication for anticoagulation. Refer to BCSH guidelines.

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Turnaround Time

Within 1 hour

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Testing Frequency

Daily/continuous processing 24hrs

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External Notes

The accuracy of all coagulation tests is greatly influenced by pre analytical variables. It is essential that sample quality is given the highest of priorities. Samples which fail to meet quality criteria including age of sample, specimen fill ( >90% ), haemolysed, clotted or activated samples will be rejected and a repeat sample requested.

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Please note: the above information is subject to change and we endeavour to keep this website up to date wherever necessary.