Unexplained differences between hospital and mortality data indicated mistakes in death certification: an investigation of 1,094 deaths in Sweden during 1995

Objective: Mortality statistics are important for epidemiological research. We examine if discrepancies between death certificate (DC) and hospital discharge condition (HDC) indicate certification errors. Study Design and Setting: From 39,872 hospital deaths in Sweden in 1995, we randomly selected 600 cases, where DC and HDC were incompatible, and 600 compatible controls, matched on sex, age, and underlying cause of death. We obtained case summaries for 1,094 (91%) of these. Using a structured protocol, we assessed the accuracy of DCs. Results: Regression analysis indicated diagnostic group and case or control as the variables that most affected the accuracy. Malignant neoplasm controls had the highest accuracy (92%), and benign and unspecified tumor cases, the lowest (20%). For all diagnostic groups except one, compatible controls had better accuracy than incompatible cases. The exception, chronic obstructive lung disease, had low accuracy for both cases (54%) and controls (52%). Conclusion: Incompatibility between DC and HDC indicates a greater risk of certification errors. For some diagnostic groups, however, DCs are often inaccurate even when DC and HDC are compatible. By requesting additional information on incompatible cases and all deaths in high-risk diagnostic groups, producers of mortality statistics could improve the accuracy of the statistics. (C) 2009 Elsevier Inc. All rights reserved.