Estimating disease prevalence using a population-based administrative healthcare database

Aims: In Ostergotland County, Sweden, all data on hospital care and primary healthcare (PHC) have been entered in a diagnosis-related administrative database since 1999. This database was used to estimate the prevalence of four chronic diseases and to examine the capture of data in PHC, outpatient hospital care, and inpatient hospital care, considered in different time frames. Methods: A case-finding algorithm identified patients with at least one healthcare contact involving a diagnosis of diabetes, hypertension, asthma, or chronic obstructive pulmonary disease (COPD) in 1999-2003. Prevalence rates were calculated as the ratio of the number of identified patients alive to the total number of inhabitants on 31 December 2003 (n approximate to 415,000). Results: Prevalence rates were 4.4% for diabetes, 10.3% for hypertension, 4.5% for asthma, and 1.2% for COPD. For all four diagnoses, the proportions of patients identified on only one healthcare level were greatest for PHC, reaching rates of 23%, 68%, 53%, and 48%, respectively. The cases identified solely in PHC comprised larger proportions of women and patients over the age of 65 years. Considering the proportion of patients identified in 2003 in relation to the total five-year period gave values of 71%, 50%, 38%, and 58%, respectively, for the four diagnoses. Conclusions: The administrative healthcare databases in Sweden today can be important tools in epidemiological research. However, data on several consecutive years and both PHC and hospital data are needed to achieve valid prevalence estimates.