A preliminary analysis of differences in coded data from Australia and Maryland.

Hospital discharge data from Maryland in the United States have many more diagnosis and procedure codes compared with coded data from Australia. In order to investigate the source of these additional codes, we analysed 4000 records from each country. There were few differences in the two samples for age, sex or number of deaths. For procedures, an important source of difference was that Maryland coders used many more diagnostic and non-surgical codes compared with Australian coders. Despite significant differences for many of the disease categories, it was not possible to learn many lessons from the Maryland data because nearly half of these codes were not related to the categories we selected for the study. For diagnoses, further work is needed to understand the differences in the number of codes used in the two countries.