Extended INR Test Intervals Safe for Warfarin-Treated Patients

Similar number of out-of-range next INR values for patients with, without extended testing interval
Similar number of out-of-range next INR values for patients with, without extended testing interval

(HealthDay News) — For stable warfarin-treated patients, extended international normalized ratio (INR) testing can be successfully and safely implemented, according to a study published online May 15 in the Journal of Thrombosis and Haemostasis.

Geoffrey D. Barnes, M.D., from the University of Michigan in Ann Arbor, and colleagues identified patients as being eligible for extended INR testing based on prior INR value stability and minimal warfarin dose changes from 2014 to 2016 at six anticoagulation clinics. The frequency with which anticoagulation clinic providers recommended an extended INR testing interval (more than five weeks) to eligible patients was assessed.

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The researchers identified at least one eligible period for extended testing in 26.5 percent of 3,362 warfarin-treated patients. There was an increase in the use of extended INR testing in eligible patients from 41.8 percent in 2014/Q1 to 69.3 percent in 2016/Q4. A similar number of subsequent out-of-range next INR values was seen for eligible patients who did and did not receive an extended INR testing interval (27.3 and 28.4 percent, respectively). There was no between-group difference in the number of major bleeding events; eligible patients with extended versus non-extended INR testing intervals had lower rates of clinically relevant non-major bleeding (0.02 versus 0.09/100 patient-years) and emergency department visits (0.07 versus 0.19/100 patient-years).

"Extended INR testing for stable warfarin patients can be successfully and safely implemented in diverse, practice-based anticoagulation clinic settings," the authors write.

Several authors disclosed financial ties to pharmaceutical and health insurance companies, including Blue Cross Blue Shield of Michigan, which funded the study.

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