Usage of the .9 codes of the ICD-10 for Japanese mortality statistics

Area of Science:

• Public Health
• Medical Informatics
• Biostatistics

Background:

• The International Statistical Classification of Diseases and Related Health Problems, Tenth Revision (ICD-10) is crucial for global health statistics.
• Application of the ICD-10 system, particularly its four-character subcategories, has faced scrutiny regarding data accuracy and usability.
• Previous research has highlighted potential biases and limitations in disease classification systems.

Purpose of the Study:

• To investigate structural deficits and application problems within the ICD-10 system in Japan.
• To examine mortality statistics for bias in death cause classification, focusing on the prevalence of unspecified codes (.9).
• To assess the quality of death certificate data and its impact on mortality statistics.

Main Methods:

• Analysis of mortality statistics in Japan from 1995 to 2007.
• Examination of death cause proportions classified using ICD-10 four-character subcategories.
• Specific focus on the distribution of cases coded under .9 (unspecified) subcategories for major causes of death.

Main Results:

• A significant proportion of deaths attributed to major causes were classified under unspecified (.9) ICD-10 subcategories.
• For instance, 97.6% of deaths classified as acute myocardial infarction (I21) were coded as unspecified (I21.9).
• This pattern suggests poor data quality on many death certificates.

Conclusions:

• The current application of ICD-10 fourth-digit subcategories in Japan may not accurately represent mortality data and actual causes of death.
• Future research should aim to reduce discrepancies between ICD terms and clinical practice.
• Physician education on accurate death cause recording is essential for improving mortality statistics.