Randomized trial of lottery-based incentives to improve warfarin adherence

Abstract

Poor adherence to medications is a major cause of morbidity and inadequate drug effectiveness. Efforts to improve adherence have typically been either ineffective or too complex to implement in clinical practice. Lottery-based incentive interventions could be a scalable approach to improving adherence. This was a randomized, controlled clinical trial of a daily lottery-based incentive in patients on warfarin stratified by baseline international normalized ratio (INR). The trial randomized 100 patients to either a lottery-based incentive or no lottery intervention. Main outcome was out-of-range INRs. Over 6 months, the overall percentage of out-of-range INRs did not differ between the 2 arms (mean 23.0% in lottery arm and 25.9% in control arm, adjusted odds ratio [OR] 0.93, 95% CI 0.62-1.41). However, among the a priori subgroup with a baseline INR below therapeutic range, there was a significant reduction in out-of-range INR in the lottery arm versus the control arm (adjusted OR 0.39, 95% CI 0.25-0.62), whereas there was no such effect among those with therapeutic INRs at baseline (adjusted OR 1.26, 95% CI, 0.76-2.09, P value for interaction = .0016). Among those with low INR at baseline, there was a nonsignificant 49% reduction in the odds of nonadherence with the intervention (OR 0.51, 95% CI 0.23-1.14). Although a lottery-based intervention was not associated with a significant improvement in anticoagulation control among all study participants, it improved control among an a priori group of patients at higher risk for poor adherence.