Frequency of monitoring INR measurements and intensity of anticoagulation

Abstract

Patients have regular blood tests to monitor their International Normalized Ratio (INR), while taking Warfarin. Patients should also know their Warfarin (Coumadin) dosage and their INR, like the way they know their blood pressure numbers. The INR is about 1.0 in healthy subject while for anticoagulant dependent patients, the INR typically should be between 2.0 and 3.0 for patients with atrial fibrillation, or between 3.0 and 4.0 for patients with mechanical heart valves in accordance with old suggestions. According to the new findings about the relationship between INR and different complications (including death), there has been a trend towards lower target intervals [7] [8]. However, different results have been obtained by simulations when the time interval of INR measurements varies between 21, 18, 15, 12, 9, 6 and 3 days in order to optimize the INR range of 2 to 3 in patients who take blood thinners steadily. In our analysis we have not been able to take different variables into account, but we are convinced that it is important for the doctor or any dose monitoring person to be aware of different changes. The results of simulations in this study indicate that more frequent measurements and adjustment of dose could decrease the variation of INR substantially. Recent analyses of risk say that smaller variation is related to lower risk of death, stroke, bleedings and hospitalization. The existence of point of care units for measuring INR at home makes more frequent measurements realizable.