MULTIPLE CAUSE-OF-DEATH DATA AS A TOOL FOR DETECTING ARTIFICIAL TRENDS IN THE UNDERLYING CAUSE STATISTICS - A METHODOLOGICAL STUDY

The aims of the study were: (i) to identify trends in the underlying c ause-of-death statistics that are due to changes in the coders' select ion and coding of causes, and (ii) to identify changes in the coders' documented registration principles that can explain the observed trend s in the statistics. 31 Basic Tabulation List categories from the Swed ish national cause-of-death register for 1970-1988 were studied. The c oders' tendency to register a condition as the underlying cause of dea th (the underlying cause ratio) was estimated by dividing the occurren ce of the condition as underlying cause (the underlying cause rate) wi th the total registration of the condition (the multiple cause rate). When the development of the underlying cause rate series followed more closely the underlying cause ratio series than the multiple cause rat e series, and a corresponding change in the registration rules could b e found, the underlying cause rate trend was concluded to be due to ch anges in the coders' tendency to register the condition. For thirteen categories (fourteen trends), the trends could be explained by changes in the coders' interpretation practice: five upward, four insignifica nt, and five downward trends. In addition, for three categories the tr ends could be explained by new explicit ICD-9 rules.