ASSESSMENT OF HCFAS 1992 MEDICARE HOSPITAL INFORMATION REPORT OF MORTALITY FOLLOWING ADMISSION FOR HIP-ARTHROPLASTY

Objective. The Health Care Financing Administration (HCFA) produced an nually from 1987 through 1994 mortality data information as part of th e Medicare Hospital Information Project (MHIP) report. We assessed the validity of these data for hip arthroplasty for one state Medicare po pulation and we analyzed the accuracy of the predictions derived from the Bailey-Makeham mortality model for this procedure. Data Sources an d Study Setting. The study sample consisted of claims and model data f rom 1,421 Medicare patients who underwent hip arthroplasty at acute ca re Arkansas hospitals from October 1990 through September 1991. Study Design. Patients were stratified into two groups based on reason for s urgery (fracture status): reconstruction or fracture management. Patie nt survival experience was compared between the two groups. The effect of fracture status on the HCFA model's predictive ability was examine d empirically and via a simulation study. Results. Our results indicat e that hip arthroplasty patients are not uniform with regard to outcom e, depending on the reason for the surgery. Patients with fracture had a much higher 30-day mortality rate than those who underwent reconstr uction (p <.001). The empirical data and the simulation study suggest that the Bailey-Makeham model underestimates mortality for reconstruct ive surgery in fracture patients, providing a false benchmark for thos e institutions that perform hip arthroplasty on predominantly one cate gory of patients. Conclusion. Published HCFA data concerning mortality for hip arthroplasty combines two different patient populations into one statistic. Casual examination of these data could result in a fals e benchmark for analysis of institutional performance. An important im plication from this study for policymakers who base decisions on ''rep ort cards'' or performance measurement reports is that, although they are necessary, generic case-mix, comorbidity, and severity of illness adjustments may not be sufficient to achieve accurate representations of outcomes, and that more disease/procedure-specific adjustments may be needed to avoid inappropriate conclusions.