Estimating chronic disease prevalence among the remote Aboriginal population of the Northern Territory using multiple data sources

Objective: To determine the prevalence rates of hypertension, diabetes, ischaemic heart disease (IHD), renal disease and chronic obstructive pulmonary disease (COPD), and their co-occurrence among the remote Aboriginal population of the Northern Territory (NT) in 2005. Methods: Information from a primary care chronic disease register (CDR) and hospital inpatient database were linked to a population list by using a unique patient identifier. A capture-recapture method (CRM) and multivariate log-linear models were then applied to analyse the multiple datasets to estimate the prevalence rates for the selected diseases and case ascertainment in each data source. Results: The NT remote Aboriginal communities had considerably higher prevalence rates across all five chronic diseases than national health survey figures. At ages 50 years and over, the prevalence rates for hypertension and renal disease were above 50%, diabetes 40%, COPD 30% and IHD above 20%. In terms of data completeness, CDR and hospital sources were both relatively incomplete, generally around 20-60%. The most common co-occurrences for the five chronic diseases were between hypertension, diabetes, IHD and renal disease. Conclusions and implications: The prevalence rates calculated using this method are comparable to estimates from rigorous small area studies, but are markedly higher than those from single clinical data sources. The results indicate that there is a considerable under-diagnosis of preventable chronic diseases in the Aboriginal communities.