Hospital discharges in New Zealand 1991-2005: changes over time and variation between districts.

AIM: This paper describes changes in the rate of hospital discharges in New Zealand between 1991 and 2006, and assesses variation across districts; it contributes to the discussion of the adequacy of the health system. METHODOLOGY: Data on public hospital discharges were obtained from the NZ Health Information Service. Diagnostic Related Groups were used to group and weight cases; domiciliary codes were used to assign cases to districts and as an indication of patients' socioeconomic status. The Intervention Ratio was used as a relative measure of national hospital throughput from 1991 to 2005, and of district service volume. The Coefficient of Variation was used as a measure of overall system variation. RESULTS: There has been an increase of 50.5% in weighted discharges from public hospitals between 1991/2 and 2005/6; adjusted for population change the increase is 17.9%. There has been a modest fall in the degree of variation between districts, but in medicine and surgery 24% of district departments appear to have levels of discharge significantly above or below the national average. CONCLUSIONS: The intensity of public hospital care to the New Zealand public has increased. Where services are provided at a level above or below the national average, local explanations should be sought and corrective action undertaken if warranted.