European study of the certification and coding of causes of death of six clinical case histories of diabetic patients. EURODIAB Subarea C Study Group.

This study was designed to investigate the large differences in diabetes mortality rates in Europe. In each of the participating countries (France, Germany, The Netherlands, Northern Ireland-UK, Republic of Ireland, Romania, Scotland-UK, Switzerland) a random sample of certifying physicians was asked to certify the causes of death of six case histories which described the deaths of diabetic patients; the responses from an average of 220 physicians per country were analysed. These registered causes were then coded nationally and the underlying cause was compared with that following a central recoding. Overall 28% of the physicians surveyed recorded diabetes on the death certificate as the underlying cause of death--France was 25% below this overall average and Germany 21% above. The national coding of diabetes as the underlying cause of death differed from the central recoding with a comparative undercoding of almost 40% in Romania, 30% in Northern Ireland and 25% in Switzerland; in contrast, there was an overcoding of diabetes by 80% in The Netherlands and 60% in the Republic of Ireland. After adjusting for central recoding, in part an adjustment for certification habits, the national coding from this simulation study was able to explain 35% of the variation in the diabetes mortality rates. With such differences in the coding of diabetes, the currently published mortality rates for diabetes are not directly comparable between European countries; some suggestions are made for the reduction of the intercountry differences in the collection and analysis of mortality data for diabetes.