A medical cause of death validation study of adult Aboriginal deaths in the Northern Territory of Australia in 1992

Judged on the criterion of equity, premature adult Aboriginal mortality is the most serious public health problem faced in Australia today. There have been a number of published epidemiological studies that have analysed Aboriginal cause of death data, but this is the first study to formally validate such data. The study sample included all adult Aboriginal people who lived and died in the Northern Territory in 1992, excluding residents of the Alice Springs region. The appropriateness of underlying cause of death codes was assessed by a single reviewer in light of death certificates, medical records, postmortem records and interviews with key health professional informants. Data were collected on 220 deaths. 8% (17 out of 220) of deaths were classified erroneously at the ICD-9 chapter level. Errors in death certification accounted for 64% (11 out of 17) of the chapter errors and diagnostic and coding errors for 18% (3 out of 17) each. The overall impact on mortality statistics was less severe because some cross-chapter classification errors cancelled each other out. Misclassification errors aggregated mainly in chapter VII (circulatory diseases) of the ICD-9 classification which was overcounted by 3.2%, and chapter VIII (respiratory diseases) which was overcounted by 1.3%. Before correction for misclassification error, circulatory diseases were judged to cause the highest proportion of deaths, whereas after correction, respiratory diseases accounted for the highest proportion. Despite this, the overall quality of the medical cause of death statistics was of a sufficiently good standard from a public health perspective to broadly inform health policy. Future attempts to improve the validity of medical cause of death statistics for Australian Aboriginal people should focus on the education of medical practitioners about the purpose and process of death certification.