The implementation of an automated coding system for cause-of-death statistics.

Background : The production of cause-of-death statistics requires the coding and selection of an underlying cause of death from death certificates. Nowadays, this is done manually in many countries around the world. However, automated coding systems have been available since the 1970s and more and more countries are switching from manual to automated coding. The introduction of an automated coding system is expected to change the coding process and its outcomes in a fundamental way. Therefore, we studied the implementation of such a system, called IRIS, in the Netherlands. Methods : We adapted the system to our situation step-by-step and measured the number of death certificates processed without any manual intervention. Medical coders analyzed and qualified death certificates that could not be processed by the system. We also performed a bridge (double) coding study on a set of death certificates so that we could compare the underlying cause of death assigned by IRIS with the underlying cause of death assigned by a medical coder to the same death certificate. Results : IRIS could handle 68.5% of the death certificates without any manual intervention. Of the (31.5%) rejected death certificates, the main reasons for rejection were the following: editing and/or coding problems (76%), not able to select an underlying cause of death (12%), ambiguous causal connection between codes (5%), a combination of the reasons mentioned (7%). In the bridge coding study, 78% of the death certificates coded by IRIS without any manual intervention showed exactly the same underlying cause of death (ICD-10, four digits) as death certificates coded manually. Conclusions : An automated coding system for causes of death reduces the workload for medical coders considerably. When editing or coding problems can be solved the system is expected to handle up to 85% of the death certificates without manual intervention. The performance of the system is strongly dependent on the quality of death certificates. A change from manual to automated coding brings about changes in the frequency of occurrence of major causes of death. Users of death statistics should be aware of these changes when studying trends in time or regional variations of causes of death.