Feasibility of Extended‐interval Follow‐up for Patients Receiving Warfarin

Abstract

Summary Aims The 2012 American College of Chest Physician Evidence‐Based Management of Anticoagulant Therapy guidelines suggest an international normalized ratio (INR) testing interval of up to 12 weeks, rather than every 4 weeks, for patients with consistently stable INRs while taking vitamin K antagonists. We aimed to examine the feasibility of extended‐interval follow‐up in a real‐world setting. Methods Patients receiving stable warfarin therapy for ≥12 weeks at baseline began extended‐interval follow‐up with visits occurring at 6 weeks, 14 weeks, and every 12 weeks thereafter to a maximum of 68 weeks or until they were no longer suitable for extended‐interval follow‐up. A single INR excursion >0.3 from goal was permitted if a reversible precipitating factor was identified and the INR was expected to return to goal without dose adjustment. The primary outcome was the proportion of patients completing all study follow‐up visits. Results Of 48 patients enrolled, 47 had evaluable data. The most common indication for anticoagulation was atrial fibrillation/flutter (53.2%). At baseline, mean prior warfarin treatment duration was 6.7 ± 6 years and median number of weeks on a stable regimen was 24 weeks (IQR, 19–37.5). Eleven patients (23%) completed all study follow‐up visits, whereas 17 (36%) did not maintain a stable INR past the 14‐week follow‐up. Conclusion A large proportion of patients with previously stable (≥3 months) INRs were not able to maintain stable INRs during extended‐interval follow‐up. More research is needed to identify patient characteristics predictive of success with extended‐interval follow‐up prior to broad implementation.

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

“…While this was unexpected from our hypothesis given the prior warfarin dose stability of participants, it is consistent with prior literature that an increase in comorbidities can decrease INR stability [17,18]. Additionally, Carris et al found only 23% of participants able to receive 12-week INR follow-up intervals for a year [12].…”

“…Our study advocates the use of a detailed protocol to safely extend the INR interval and offers guidance on longer-term use of an extended INR interval to complement what previous literature has described [12,13]. Our study found that by titrating the INR followup interval up to 12 weeks we could identify individuals who could not maintain an extended INR interval despite a previous history of warfarin dose stability.…”

“…Many clinicians in the United States use 4-6 week INR follow-up intervals for these patients [8][9][10]; however, the 2012 American College of Chest Physicians' guidelines suggested a 12week INR follow-up interval may be appropriate [11]. An extended INR follow-up interval has the potential to decrease cost and workload for both the healthcare system and patients [12].…”

“…However, all patients were contacted by their warfarin provider every 4 weeks regardless of their randomization status. Carris et al implemented a 12-week INR follow-up interval for a maximum of 68 weeks and found that few patients were able to maintain a 12-week interval [12]. Patients with nontherapeutic INRs, considered to be > 0.3 away from goal, warfarin dose changes, and shorter follow-up intervals required were removed from further observation in the study after the initial visits.…”

Barriers and facilitators to reducing frequent laboratory testing for patients who are stable on warfarin: a mixed methods study of de-implementation in five anticoagulation clinics

“…One other health system has published their experience with a similar de-implementation effort to reduce frequent INR tests among patients with stable warfarin control [16, 17]. However, they did not report on how frequently their staff scheduled the next INR test more than the standard 4 weeks into the future for eligible patients or the barriers and facilitators to their de-implementation effort.…”