To our best knowledge, this is the first study in China using interrupted-time series design to evaluate the impact of DRGs-based ISM policy on the performance of regional inpatient services. We also firstly look at the impact of DRGs-based ISM policy in a regional scale rather than in hospital level. As shown in the results, after implementing ISM policy, the performance of regional inpatient service has changed as follows. In capacity dimension, first, the DRGs number did not change significantly, indicating that the type of diseases in Jiading District did not change much. Second, that the trend of CMI changed from decreasing to increasing indicated an increase in the regional medical resource consumption and it may due to that the complexity of cases in this region have increased. Finally, the accelerated growth of total weight showed that the increase of total inpatient service output in this region was accelerated. In efficiency dimension, the larger negative slope for TEI showed fastened decrease in the length of stay. The trend of CEI changed from upward to downward showing that the implementation of ISM policy not only controlled the increase of cost but also tended to reduce the cost. In quality dimension, despite an accelerated decline trend was found in IMLRG and IMMLRG, there was no statistical significance. This may indicate that ISM policy has not introduced significant effect on service quality by the time of evaluation.
To our best knowledge, the majority of our study results are consistent with results from previous studies in other countries. In the United States, CMI was found to be improved rapidly after the DRGs payment reform in 1980. Some studies believe that this improvement in CMI is owed not only to the implementation of DRGs-based payment system but also to the updated coding system induced by the incentive mechanism [24]. Since the results of ISMS was used as a basis for deciding government investment to hospitals rather than as a payment system in this study, accounting for about 10% of the hospital income, the impact of economic incentive should be limited. In this case, the improvement of CMI in this study may be largely due to the increased complexity of diseases, indicating that ISM policy could potentially improve the service capacity of the hospitals. According to experience from European countries, under DRGs-based payment system, hospitals have a strong incentive to increase service volumes [12]. Similarly, the accelerated growth of total weight found in this study indicates an increase in service volumes. As to efficiency dimension, the experience from the United States and European countries [12, 13] both showed that there was a significant decline in the length of stay, but the impact on medical costs were different with some studies demonstrating a decreased growth rate while others showing no effect in cost control. In our study, a significant decrease was found not only in the length of stay, but also in medical costs, indicating the important role of ISM policy in cost control. In terms of quality dimension, several studies [12, 25] have shown that DRGs had little effect on improving quality of service. Although the service quality was not improved significantly in this study, a downward trend in mortality rate was observed. If we continue to collect data, there may be significant effects in the long run.
Currently, the health care system in most countries is dominated by public hospitals, so the management of public hospitals is an issue that all governments should pay attention to. The ISM policy, as demonstrated in our study, could be an effective way to improve inpatient service performance of public hospitals through the following ways. Starting from multiple aspects, the ISM policy could improve the hospital transparency, inform government to make effective investment, enhance the hospital motivation and competition, and eventually achieve the goal of improving the performance of regional inpatient service. First, the implementation of DRGs-based ISMS, to predict the number of cases in the region and estimate the total cost, could improve hospital transparency and make it easier for government to manage public hospitals. Second, the regular supervision by quality control team on the EMR data from each hospital reduces information asymmetry. Third, the application of the evaluation and incentive mechanism by linking the results of performance evaluation to government investment to each hospital ensures the government’s full understanding of regional inpatient service performance, rewards desired hospital performance and therefore enhances hospital motivation. Moreover, it enhances the competition between hospitals by publicizing the performance of each hospital. Lastly, the data covered in ISMS helps government to better understand the development of different disciplines in each hospital therefore informs the government investment aiming to overcome the hospital shortcomings and strengthen the predominant disciplines. There are three prerequisites for implementing ISM policy including a good information system, high-quality EMR data, and a management team. With these three prerequisites, other countries could also implement their own ISM policy to help government manage public hospitals and improve the performance of regional inpatient service.
There are some limitations in this study. First, limited by time span of the data, we used quarterly data rather than annual data to ensure enough data points, but using quarter as the unit may affect the interpretation of the level change since the influence of different quarter on level change was unavoidable. As we can see from the results, the level change of most indicators was the opposite of expectation, it might be explained by the fact that there was a seasonal difference between the first quarter of 2017 and the fourth quarter of 2016. Second, as the DRGs classification system was improved and the weight was adjusted in 2019, it may have some impact on the comparability of the data of performance indicators in 2019 with the data in 2013–2018. However, considering that no major adjustment was made, the impact should be minor. Finally, as China's health reform has lasted for 10 years [26], and a number of reforms have been launched, such as zero mark-up drug and drug pricing negotiations [18, 27]. These policies may also have some impact on the performance indicators evaluated in our study, enlarging or distorting our research results.