Accuracy of a Portable International Normalized Ratio Monitor in a Population Aged 75 Years Old and Over

Adverse effects of oral anticoagulants (warfarin, fluindione mainly) are bleeding complications and concern 13% of hospitalizations, approximately 17,000 admissions per year. They constitute 12.3% of iatrogenic adverse effect according to the latest results of the survey conducted by the haute autorité de santé (HAS). A study realized in 2000, with 2976 patients, shows that 28.8% of patients were outside of any therapeutic range (<2 or> 4.5). In 2003, a third of french biologists had no knowledge of the indication of VKA treatment of patients at the INR measurement, and more than fifty percent in 2000. When the therapeutic range was known, the value of the INR remained outside it in 30% of cases. The median time between INR equilibration phase was 5 to 6 days, while the recommended time is 2 to 4 days. A quarter of patients in phase equilibrium treatment did not have a measure of INR at least once a month. Followed over a period of a year, patients spent 40% of the time with a value of INR outside the therapeutic range, high-risk area of recurrent thrombosis or hemorrhage. That is why they require regular monitoring of INR.

Currently, this monitoring is done through a blood sample analyzed by a laboratory according to standard techniques.

The use of the INR measurement by capillary method provides a result in less than 3 minutes. This also allows the development of different monitoring strategies. In the context of a self-monitoring measure, the patient himself performs the test using the device and therapeutic adjustment is made by the health care professional.

Data analysis by HAS showed that the use of a self-measurement device significantly improved the time spent in the therapeutic range, reduced the risk of major bleeding and the accident major thromboembolism.

The pathologies treated by VKA are more common in the elderly. They are also more vulnerable to falls, overdoses of these treatments because their pharmacokinetics is amended by polypharmacy, malnutrition, less protein binding. The relative risk of bleeding is multiplicated by two beyond 70 years. Despite the emergence of new anticoagulants in the prevention of complications of arrhythmia (this disorder affect nearly 10% of the population aged over 80 years), VKA remains prevalent because these new drugs have renal elimination that can not be monitored, and can not be dialysable, have no antidote and represent a daily cost about 30 times the VKA.