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

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.

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.

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.

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.