Prospective Evaluation of an Extended Interval of INR Follow-up in a VA Anticoagulation Service

The purpose of this study is to determine the feasibility, safety, and acceptability of implementing an extended interval of INR follow-up in Veterans on a stable dose of warfarin in the Anticoagulation Clinic at the William S. Middleton Memorial Veterans Hospital.

All participants will be provided usual care from the anticoagulation clinic, except for the interval between INRs. If the participant continues to be on a stable dose of warfarin and the INRs are within the goal range of 2-3 (including lab variation), follow-up visits will be scheduled following an extended interval protocol, from 5-6 weeks, to 7-8 weeks, to 11-12 weeks and then continued with 11-12 week visits if INRs continue to remain in goal range and appropriate for the patient. Patient satisfaction will be evaluated at baseline, 6-, 12-, and 24-months. Additionally provider satisfaction, confidence, and knowledge of the extended interval protocol will be analyzed. Bleeding and thromboembolic events will be evaluated to ensure the safety of an extended follow-up interval.

Inclusion criteria

• 18 years of age or older
• requirement for indefinite warfarin therapy
• target INR of 2-3
• stable weekly warfarin dose for the past 6 months (not more than a single, one-time adjustment (boost/omission) in the past 6 months, planned interruption for a procedure or surgery with INR(s) out of range in the past 6 months would not exclude a patient)
• a patient of the Madison VA anticoagulation clinic for the previous 12 months

Exclusion criteria

• consistently drink ≥4 alcoholic beverages/day or a documented episode of alcohol binging in the past 6 months
• diagnosis of cancer and on active chemotherapy/radiotherapy in the past 3 months
• life expectancy of < 1 year
• enrolled in other investigational drug protocols
• only receiving anticoagulation care at the Madison VA for part of the year (e.g. snowbirds)
• receiving visiting nurse services for INR monitoring
• thrombocytopenia (<100K) within past 12 months
• history of bleeding or thromboembolism requiring medical intervention within past 6 months
• treatment for active liver disease (e.g. hepatitis)
• diagnosis or documentation in EMR suggesting cognitive impairment
• activated power of attorney
• inability to provide informed consent
• non-English speaking
• unstable mental health disorder that impairs judgment
• history of non-adherence to anticoagulation clinic policies and procedures (i.e. missed appointments, self-adjustment of warfarin dose, nonadherence, etc.).