Accuracy of cause-of-death coding in Taiwan: types of miscoding and effects on mortality statistics

Background The objectives of this study were to assess the accuracy of caus e-of-death coding, determine the extent to which coders follow the selectio n rules of coding set out in the International Classification of Diseases, 9th Revision (ICD-9), and the effects of miscoding on mortality statistics in Taiwan. Method A systematic sample of 5621 death certificates was reviewed. The und erlying cause of death (UCD) selected by the reviewer for each death certif icate was compared with that selected by the original coder. The UCD was se lected according to ACME (Automated Classification of Medical Entities) Dec ision Tables. Results The overall agreement rates between the reviewer and coders accordi ng to the three-digit and two-digit categories of ICD-9 were 80.9% and 83.9 %, respectively. Good agreement was found for malignant neoplasms (kappa = 0.94) and injuries and poisoning (kappa = 0.97), but there was poor agreeme nt for nephrotic dis eases (kappa = 0.74), hypertension-related diseases (k appa = 0.74), and cerebral infarction (kappa = 0.77). Reasons for disagreem ents included disagreement in nomenclature (42.8%), inappropriate judgement of causal relationships (41.5%), and incorrect interpretation of Selection Rule 3 and Modification Rules (15.7%). Conclusion This study showed various levels of agreement for different dise ases between the reviewer and the original coders in selection of the UCD. Owing to the 'compensatory effect of errors', the national mortality statis tics were not affected significantly. The national administration should un dertake routine internal studies to control the quality of UCD coding pract ices.