December 1, 2008BMC Health Services Research268 citationsOpen Access
A test of financial incentives to improve warfarin adherence
Key Result
A daily lottery-based financial incentive reduced the mean proportion of incorrect warfarin doses to 2.3% and 1.6% in two pilot studies, compared to a historic mean of 22%.
Structured PICO
Does a daily lottery-based financial incentive improve warfarin adherence and time in therapeutic INR range in patients on chronic warfarin therapy?
P
Population
20 adult patients (≥21 years old) who had been taking warfarin for at least 3 months, receiving care at the University of Pennsylvania Anticoagulation Management Center.
I
Intervention
Daily lottery-based financial incentive (expected value of $5 per day in Pilot 1, $3 per day in Pilot 2) contingent on opening a computerized pillbox (Informedix Med-eMonitor System) to take warfarin, plus a daily reminder chime, administered over 3 months.
C
Comparator
Within-subject pre-intervention historical controls (prior MEMS cap adherence data or prior INR measurements) and clinic population historical means.
O
Outcome
Proportion of incorrect warfarin doses (patient adherence).surrogate
A daily lottery-based financial incentive significantly improved warfarin adherence and time in therapeutic INR range, though effects diminished after the intervention ended.
Main Result
Absolute Event Rate: 2.3% vs 22%
Limitations
- Not conducted as a randomized controlled trial
- Small sample size
- Short duration of follow-up
Abstract
BACKGROUND: Sub-optimal adherence to warfarin places millions of patients at risk for stroke and bleeding complications each year. Novel methods are needed to improve adherence for warfarin. We conducted two pilot studies to determine whether a lottery-based daily financial incentive is feasible and improves warfarin adherence and anticoagulation control. METHODS: Volunteers from the University of Pennsylvania Anticoagulation Management Center who had taken warfarin for at least 3 months participated in either a pilot study with a lottery with a daily expected value of 5 (N = 10) or a daily expected value of 3 (N = 10). All subjects received use of an Informedix Med-eMonitor System with a daily reminder feature. If subjects opened up their pill compartments appropriately, they were entered into a daily lottery with a 1 in 5 chance of winning 10 and a 1 in 100 chance of winning 100 (pilot 1) or a 1 in 10 chance of winning 10 and a 1 in 100 chance of winning 100 (pilot 2). The primary study outcome was proportion of incorrect warfarin doses. The secondary outcome was proportion of INR measurements not within therapeutic range. Within-subject pre-post comparisons were done of INR measurements with comparisons with either historic means or within-subject comparisons of incorrect warfarin doses. RESULTS: In the first pilot, the percent of out-of-range INRs decreased from 35. 0% to 12. 2% during the intervention, before increasing to 42% post-intervention. The mean proportion of incorrect pills taken during the intervention was 2. 3% incorrect pills, compared with a historic mean of 22% incorrect pill taking in this clinic population. Among the five subjects who also had MEMS cap adherence data from warfarin use in our prior study, mean incorrect pill taking decreased from 26% pre-pilot to 2. 8% in the pilot. In the second pilot, the time out of INR range decreased from 65. 0% to 40. 4%, with the proportion of mean incorrect pill taking dropping to 1. 6%. CONCLUSION: A daily lottery-based financial incentive demonstrated the potential for significant improvements in missed doses of warfarin and time out of INR range. Further testing should be done of this approach to determine its effectiveness and potential application to both warfarin and other chronic medications.