Application of Regression-Discontinuity Analysis in Pharmaceutical Health Services Research

Authors

  • Ilene H. Zuckerman,

  • Euni Lee,

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    • Address correspondence to Euni Lee, Pharm.D., Ph.D., Center for Minority Health Services Research, Department of Clinical and Administrative Pharmacy Sciences, School of Pharmacy, Howard University, 2300 Fourth Street, NW, Washington, DC, 20059-0001. Ilene H. Zuckerman, Pharm.D., Ph.D., and Bruce Stuart, Ph.D., are with the Department of Pharmaceutical Health Services Research, School of Pharmacy, University of Maryland, Baltimore, MD. Anthony K. Wutoh, Ph.D., and Zhenyi Xue, M.S., are with the Center for Minority Health Services Research, Department of Clinical and Administrative Pharmacy Sciences, School of Pharmacy, Howard University, Washington, DC.

  • Anthony K. Wutoh,

  • Zhenyi Xue,

  • Bruce Stuart


Abstract

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<.001) according to the repeated-measure ANOVA and by 0.2 canisters per month (p<.001) from RD analysis.

Conclusions. Regression-discontinuity design is a useful quasi-experimental methodology that has significant advantages in internal validity compared to other pre–post designs when assessing interventions in which subjects' assignment is based on cutoff scores for a critical variable.

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