Medical College of Wisconsin
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Feasibility and safety of a 12-week INR follow-up protocol over 2 years in an anticoagulation clinic: a single-arm prospective cohort study. J Thromb Thrombolysis 2019 Feb;47(2):200-208



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Scopus ID

2-s2.0-85055931107   5 Citations


The 2012 American College of Chest Physicians' guidelines recommended a 12-week INR follow-up interval may 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 may not be suitable for this intervention.

Author List

Porter AL, Margolis AR, Staresinic CE, Nagy MW, Schoen RR, Ray CA, Fletcher CD


Michael W. Nagy PharmD Assistant Professor in the School of Pharmacy Administration department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Ambulatory Care Facilities
Blood Coagulation
Drug Monitoring
Feasibility Studies
International Normalized Ratio
Middle Aged
Predictive Value of Tests
Prospective Studies
Risk Factors
Time Factors
Treatment Outcome
United States
United States Department of Veterans Affairs