Application of Regression-Discontinuity Analysis in Pharmaceutical Health Services Research

Objective. To demonstrate how a relatively underused design, regression‐discontinuity (RD), can provide robust estimates of intervention effects when stronger designs are impossible to implement. Data Sources/Study Setting. Administrative claims from a Mid‐Atlantic state Medicaid program were used to evaluate the effectiveness of an educational drug utilization review intervention. Study Design. Quasi‐experimental design. Data Collection/Extraction Methods. A drug utilization review study was conducted to evaluate a letter intervention to physicians treating Medicaid children with potentially excessive use of short‐acting β2‐agonist inhalers (SAB). The outcome measure is change in seasonally‐adjusted SAB use 5 months pre‐ and postintervention. To determine if the intervention reduced monthly SAB utilization, results from an RD analysis are compared to findings from a pretest–posttest design using repeated‐measure ANOVA. Principal Findings. Both analyses indicated that the intervention significantly reduced SAB use among the high users. Average monthly SAB use declined by 0.9 canisters per month (p