Medical Sociology of Hospital Payment Reform and Informal Charge Extraction in Ghanaian District Hospitals: A Difference-in-Differences Estimation of Diagnosis-Related Group Exposure and Out-of-Pocket Burden

Ghana's transition from fee-for-service to diagnosis-related group (DRG) payment in district hospitals is expected to reduce out-of-pocket burden, but informal charge extraction may offset formal savings. Evaluating such reforms requires designs that can separate policy effects from secular trends and from pre-existing differences between exposed and unexposed facilities. the present analysis characterises the operating characteristics of a before–after–control–impact (BACI) estimator for DRG exposure effects on out-of-pocket burden, using a replication-based power analysis under a declared variance structure (between-cluster SD = 6.0, residual SD = 4.5, intraclass correlation = 0.64). Power was estimated across 2000 design cells defined by 8, 16, 24 and 32 clusters and effects of 3, 5 and 8 percentage points.54 clusters are required to detect a 5-percentage-point effect at 80% power, and that the minimum detectable effect at 80% power declines steeply as cluster count rises from 8 to 32. The intraclass correlation of 0.64 implies that district-level clustering absorbs most of the variance in out-of-pocket burden, so credible inference about informal charge extraction depends less on adding patients within facilities than on adding facilities. BACI designs can support causal claims about DRG exposure only when cluster counts are adequate to the effect size of interest, and it specifies the boundary conditions under which estimates of informal charge extraction are likely to be informative.