Impact of Diagnosis-Intervention Packet Compliance Training on Inpatient Expenditures Under Case-Based Payment Reform: A Quasi-Experimental Study Based on Discharge Records.

Objective: Despite the widespread implementation of case-based payment reforms, the role of hospital-internal compliance training remains underexplored. This study examines the impact of training on inpatient expenditures under Diagnosis-Intervention Packet (DIP) reform, and explores its role as an institutional mechanism for translating top-down policy incentives into frontline clinical practice. Methods: Based on 58,411 inpatient discharge records from a tertiary hospital in Shenzhen during 2022-2024, this study adopts the administratively assigned DIP training as a quasi-experimental shock, an approach well-aligned with our causal identification framework. The event-study design explicitly identifies the dynamic temporal trend of treatment effects post-training, and the staggered difference-in-differences estimation addresses potential endogeneity by controlling for department-specific fixed effects and time trends. Results: DIP compliance training leads to sustained reductions in inpatient expenditures, with total costs decreasing by 14.5% at 12 months post-training. Significant declines are observed in drug (37.2%), laboratory (21%) and inspection (8.3%) expenditures. The effects are more obvious in coding-intensive surgical departments, accompanied by a structural shift toward service-oriented expenditure categories. Further robustness checks enhance the reliability of the empirical results. Conclusion: By improving coding competence and aligning clinical documentation with DIP grouping rules, DIP training serves as a key organizational mechanism for hospitals to internalize payment reform incentives. These findings highlight the importance of institutional capacity building for the sustainable implementation of local case-based payment reform and other health systems pursuing value-based care.