INR (International Normalized Ratio): Why and When is it Measured?

(PT). The International Normalized Ratio is used to eliminate the variability of the results obtained in the different laboratories.

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Going into more detail, INR is one of the derived measures of PT (from the English Prothrombin Time) which takes into account the sensitivity of the thromboplastin reagent used by the laboratory in order to obtain comparable results.

INR is indicated for periodic monitoring of patients on oral anticoagulant therapy. These drugs are, in fact, antagonists of vitamin K and, as such, capable of inhibiting the activation of the factors of the vitamin K dependent coagulation cascade (factors II, VII, IX and X). The determination of INR is therefore useful for ensure that the medicine is effective and the prothrombin time is appropriate.

takes longer than normal to clot;

Lower values ​​than normal indicate that the blood clots more quickly.

For this reason, the INR assessment is also prescribed when a person is taking oral anticoagulants, such as warfarin.