Home Monitoring Improves INR Control for Warfarin Patients

Patients who self-monitored their international normalized ratio weekly achieved significantly better control than those who did so less frequently, but all home monitoring patients performed well, according to in a new study.

Patients treated with warfarin who self-monitored their international normalized ratio (INR) optimized their anticoagulation therapy and spent more time in the therapeutic range, according to the results of a new study. Time in the therapeutic range was especially improved in patients who performed home monitoring on a weekly basis compared with those who did so less frequently.

The study, published online on March 18, 2014, in the American Journal of Managed Care, evaluated the quality of warfarin treatment by measuring the time in therapeutic INR range (TTR) in patients who performed home monitoring outside of a clinical trial setting. Using the database of an independent diagnostic testing facility, the retrospective analysis assessed TTR for “real-world” patients who performed home monitoring weekly or variably every 2 to 4 weeks. All patients were trained in home monitoring beginning in January 2008 and had completed at least 6 months of self-monitoring by June 2011. The results from the first 3 months of patients’ self-testing were excluded from the analysis to account for variations in the time patients needed to master home monitoring.

A total of 29,457 patients receiving warfarin therapy were included in the analysis. Overall, participants were in the therapeutic INR range 69.7% of the time, achieving a higher average TTR than has been previously reported in randomized clinical trials and meta-analyses. Participants who self-monitored less frequently than once per week were in the therapeutic INR range 68.9% of the time, while those who self-monitored weekly achieved a significantly higher TTR of 74%. The results also indicated that older patients aged 65 to 74 had a 71.5% TTR, which was significantly higher than the 67% TTR for younger patients aged 46 to 64.

Weekly testers were also more likely to achieve a greater TTR faster than those who tested less frequently. Patients who self-monitored weekly achieved an average TTR greater than 72% within their first 3 months of testing, while those who self-monitored less frequently had a lower average TTR of 65.5% after the 3-month initiation period and took 20 months longer to reach an average TTR greater than 70%. In addition, weekly testers experienced significantly fewer critical INR values than did variable testers.

However, even the patients who performed home monitoring less frequently than weekly achieved TTRs that were greater than the best TTRs among patients treated with warfarin in randomized trials of new oral anticoagulants, the authors note. Nonetheless, they point out that weekly testing appears to be the best way to optimize anticoagulation therapy and to decrease the risk of critical INR values.

“A weekly [test frequency] may represent a challenge to clinicians who are accustomed to and trained on counseling and titrating at traditional monthly intervals, but [portable point-of-care] monitoring at home makes this option easily available and manageable for both physicians and patients,” the authors conclude.