Estimating the causal effect of a quality assurance program on quality of care in Germany

Inpatient safety can benefit from effective policies for hospital quality assurance. Following legal reform to put quality of care more center stage in hospital capacity planning, a new quality assurance program was introduced in Germany in 2017. The program was based on pre-existing quality indicators and included new policy design components emphasizing hospital accountability. Learning if the policy was effective is important, but challenging in the observational setting. We adapt a quasi-experimental difference-in-differences approach to estimate the causal effect of the program on quality of care in the 4 years after program onset. A control group of indicators from other clinical areas is carefully selected to compare trends in process quality. Results show a relevant reduction in risk of adverse care events nationally in the affected patient population relative to a counterfactual scenario of no program adoption. The effect emerged over the first two program years before plateauing. The study allows to learn about important design components in healthcare quality assurance. Among our discussed mechanisms for the documented improvement in process quality are the initial announcements of legal consequences and high public attention. These led hospitals to initiate quality improvement, to seek dialogue with state agencies, and to put more efforts into submitting correct quality data. Methodologically, we show how to adapt rigorous study designs to quality assurance evaluation, considering also their assumptions and limitations.