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.


METHODS
Administrative claims from a Mid-Atlantic state Medicaid program were used to evaluate the effectiveness of an educational drug utilization review intervention.


METHODS
Quasi-experimental design.


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 beta(2)-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.


RESULTS
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.
Department of Pharmaceutical Health Services Research, School of Pharmacy, University of Maryland, Baltimore, MD, USA.
Ilene H
IH
Zuckerman
Euni
E
Lee
Anthony K
AK
Wutoh
Zhenyi
Z
Xue
Bruce
B
Stuart
D001993:Bronchodilator Agents / Q000008:administration & dosage; D002648:Child; D017723:Drug Utilization Review / Q000379:methods* / Q000706:statistics & numerical data*; D006302:Health Services Research / Q000379:methods* / Q000706:statistics & numerical data*; D006801:Humans; D008484:Medicaid / Q000706:statistics & numerical data; D010818:Practice Patterns, Physicians'; D012044:Regression Analysis
D001993:Bronchodilator Agents