feasibility and safety of a 12-week inr follow-up protocol over 2 years in an anticoagulation clinic: a single-arm prospective cohort study

The 2012 american college of chest physicians’ guidelines recommended a 12-week inr follow-up interval be appropriate for patients on stable warfarin doses. limited evidence supports this recommendation. a single-arm, prospective cohort study over 24 months was completed in a veterans affairs anticoagulation clinic to determine the long-term feasibility and safety of implementing an extended inr follow-up interval in veterans on stable doses of warfarin. participants were required to have a stable warfarin dose for 6 months prior to enrollment. a prespecified protocol was used to titrate, extend, and manage the inr interval up to 12 weeks. scheduling of extended inr intervals was a primary outcome. safety outcomes included major and serious bleeding and thromboembolic events. a post-hoc comparison of baseline characteristics between individuals who were scheduled for at least 4 consecutive 12-week inr follow-up intervals and those who were not was completed. of the 50 participants, 36 (72%) were scheduled for at least one 12-week interval and 15 (30%) were scheduled for 4 consecutive intervals. there were 2 thromboembolic events that occurred in 1 participant. there were 28 major and serious bleeding events in 19 participants; 8 occurred while on the extended inr interval. in the post-hoc analysis, no participants scheduled for 4 consecutive 12-week intervals had heart failure. based on 2 years of monitoring, a 12-week inr follow-up interval using a detailed protocol with titration of inr interval extension appears feasible for a subset of patients. patients with heart failure not be suitable for this intervention.