Accuracy of recording of deaths from asthma in the UK: The false negative rate

Background - A study was carried out to determine the extent to which asthma deaths are wrongly attributed to another cause on UK death certificates. Methods - Deaths from all causes occurring anywhere in the UK were identified amongst 2382 subjects aged 16-64 years within three years of discharge following hospital treatment for asthma (ICD9 493) in hospitals in the South East Thames region. The deaths were reviewed by an expert panel to assess the proportion of asthma deaths identified by the panel which were attributed to another cause of death on the death certificate (false negatives). Results - Eighty five deaths from all causes were identified in a mean follow up period of two years and three months. in 61 cases (72%) there was sufficient information for the expert panel to be confident about the cause of death. The panel identified 22 deaths from asthma, four of which were certified as non-asthma deaths (two as deaths from chronic obstructive pulmonary disease (COPD) and two as deaths from cardiovascular disease). The proportion of false negative death certificates was four of 22 (18%, 95% confidence interval (CI) 5 to 40). Conclusions - There is evidence that asthma deaths in the UK are wrongly certified as deaths from both chronic obstructive pulmonary disease and diseases of the cardiovascular system.