INR monitoring

INR monitoring

INR is short for International Normalized Ratio of a test called Prothrombin Time. It is also called PT-INR. The INR monitoring is used to monitor the dosage of a group of medications known as coumadin or warfarin. They prevent clotting of blood and thereby prevent certain diseases like stroke and deep vein thrombosis with subsequent pulmonary embolism. They are also used when there is an artificial heart valve inside the heart.

The target range of INR values needed depend on the reason for using it. In most cases the target INR value is 2-3. If the value obtained in the test while on medication is higher, the dose of the medication is reduced and vice versa. In certain cases, as with artificial mitral valve between the left sided chambers of the heart, a higher INR value of 2.5 to 3.5 is recommended.

Many other medications and foods interfere with the action of coumadin or warfarin. Green leafy vegetables with high vitamin K content can reduce INR. Hence whenever other medications are added or removed, it is better to recheck the INR value even if it was stable earlier. For routine monitoring a test once a month would be adequate. Usual INR testing is done using blood drawn from the vein at a laboratory.

But now devices for home INR monitoring, which can test the INR value with blood obtained from a finger prick are also available. Though these devices need an initial extra cost, they offer the convenience of INR monitoring from home, which is especially useful for those staying far away from cities where most of the labs are located.

In addition to routine monthly monitoring of INR, it is mandatory to check INR whenever any bleeding manifestation is noted so that one can reduce the dose of warfarin if the INR is high. Very high INR values, usually well above 5 are better managed in the hospital setting.