Asthma mortality in Danish children and young adults, 1973-1994: epidemiology and validity of death certificates

Abstract

Several reports indicate that asthma mortality has increased during the last few decades. International comparisons reveal some striking differences in the pattern of asthma mortality. The authors investigated the asthma mortality rate in the Danish child and youth population 1973–1994 and studied the validity of death certificates. The authors reviewed all death certificates coded as asthma death in the International Classification of Diseases (ICD 8–ICD 10 (1994)) and adjacent respiratory code numbers for the age group 1–19 yrs. Hospital records and autopsy reports were assessed to validate the cause of death. Age‐standardized and age‐specific mortality rates were calculated. From 1973 to 1987 there was a significant upward trend in the mortality. On subdivision, this trend was limited to the age group 15–19 yrs. Generally the mortality rate decreased from 1988 to 1994. Four per cent coded as asthma were false positive. Twelve per cent were false negative asthma deaths, wrongly coded as due to other causes. Only 62% of all true positive death caused by asthma were appropriately coded. The number of false negative certifications increased with increasing autopsy frequency. Asthma mortality rates in Denmark increased in adolescents during 1973–1987 and decreased from 1988 to 1994. A possible explanation may be an increased awareness of asthma symptoms combined with a steadily improved treatment of asthma. Even in children and young adults under the age of 20 yrs, validity problems still make comparisons between countries difficult; even interpretation of national trends requires caution.

Methodology of studies evaluating death certificate accuracy were flawed

“…Instead, a substantial number of studies assess how well the data suit a particular purpose. Thus, some try to assess [9,11,13,23,24,34,37,43] how well reported causes of death mirror the prevalence of a particular condition at death, whether or not it caused the death. Other studies always assign the death to a specific condition if present, regardless of the other conditions from which the decedent may have suffered.…”

“…In eight studies panel members first assigned a cause of death independently, and the panel then jointly assessed cases in which the members had assigned different causes of death. Five studies used other methods to adjudicate differences between panel members: majority decision [13,21], decision by the panel chair [22], decision by an independent specialist [23], or excluding such deaths from the analysis [24]. In four papers, the panel procedures were not described.…”

“…However, these studies do not show consistent results, and sometimes are in conflict. Whereas it is understandable that the quality of reporting may vary with cause of death [9,10], it is surprising that even studies of the same condition sometimes arrive at different conclusions [11][12][13][14]. These differences raise questions about the design of the evaluation studies and the evaluation methods used.…”

Validity of the European short list of respiratory diseases: a 40-year autopsy study

“…Respiratory diseases, except for pulmonary neoplasm [24], may have more ambiguous autopsy criteria than cardiovascular diseases or neoplasms in other organs. JøRGENSEN et al [25] stated that after autopsy and histological examination of asthma deaths in Denmark, many cases were coded by the pathologist as due to emphysema and/or bronchitis. However, E40 groups the chronic inflammatory lower respiratory diseases and may thus improve its validity.…”

Availability and quality of vital registration mortality data in South Africa: a national and surveillance site perspective

“…234,270 In their review of the methods used in studies which assessed cause-of-death accuracy of deaths reported to official mortality statistics agencies, Johansson et al found that most studies, 89%, made use of medical records. Two of these studies assessed the accuracy of asthma deaths in Denmark, 244,271 both finding that the accuracy of death certification in asthma deaths was poor. In official statistics for Warsaw in Poland, May found that mortality from 120 asthma and COPD has been underestimated when compared to hospital and clinic records.…”