Evaluation of the effect of DRG payment policy based on interrupted time series modeling: evidence from a tertiary hospital in Anhui Province

The payment methodology for diagnosis-related groups (DRG) has implications for both society and medical institutions. Our study aims to analyse the impact of the reform of the payment policy according to the DRG on the operation of a tertiary hospital in Anhui Province. Monthly data were collected from April 2020 to September 2023 during the reform period for a tertiary hospital on nine types of operational indicators, including average length of stay (ALOS), number of discharges, number of outpatient visits, percentage of discharged patients undergoing level III or IV surgery, bed turnover rate, inpatient essential drug utilization rate, low-risk group mortality, outpatient subaverage cost and inpatient subaverage cost. The data were divided into two phases according to the time of DRG implementation: pre-reform (April 2020-December 2021) and post-reform (January 2022-September 2023), and the segmented regression model with interrupted time series data was used to analyse the changes in the trend of each type of indicator before and after the reform. Statistical analysis was performed using R software (4.3.1). After the implementation of the DRG, the number of discharges increased by 112 800 patients (95% confidence interval [CI] 31.125-194.484, P = 0.008), the bed turnover rate rose by 1.403% (95% CI 1.028-1.778, P = 0.022) and the percentage of discharged patients undergoing level III or IV surgery decreased by 0.098% (95% CI -0.181 to -0.015, P = 0.022). The low-risk group mortality decreased by 0.016% (95% CI -0.027 to -0.005, P = 0.007), and the inpatient subaverage cost decreased by 81.514 CNY (95% CI -121.782 to -41.245, P