about international classification of diseases

GENERAL INFORMATION

• The World Health Organization’s International Classification of Diseases (ICD) is used to classify diseases and other health problems for health and vital records including death certificates, hospital records and emergency department visit records.
• Prior to the implementation of the currently used International Statistical Classification of Diseases and Related Health Problems (ICD-10), the International Classification of Diseases Ninth Revision (ICD-9) was used. In Ontario, ICD-10 was implemented on January 1, 2000 for death data and on April 1, 2001 for hospitalization data. Emergency department visit data has used ICD-10 since its inception.
• ICD-10 is more detailed than ICD-9 with about 8,000 categories compared to approximately 5,000 in ICD-9.
• The ICD-9 contained numeric codes categorized into 17 chapters plus two supplementary classifications: the Supplementary Classification of External Causes of Injury and Poisoning (E codes) and the Supplementary Classification of Factors Influencing Health Status and Contact with Health Services (V codes).
• In Canada, an enhanced version of the ICD-10 is maintained by the Canadian Institute for Health Information (CIHI). The International Statistical Classification of Diseases and Related Health Problems, Canada, Version 10 (ICD-10-CA) is updated periodically (i.e., every two to three years) to ensure it remains relevant in the Canadian context. The ICD-10-CA includes the addition of fifth and sixth characters to provide added specificity. ICD-10-CA also includes two additional chapters (related to the morphology of neoplasm and provisional codes for research and temporary assignment). On rare occasions codes in ICD-10 and ICD-10-CA differ slightly (e.g., HIV where ICD-10 uses codes B20-B24 whereas in ICD-10-CA only B24 is used and B20-B23 do not appear at all).
• The ICD-10-CA contains alphanumeric codes categorized into 21 chapters, and includes chapters related to external cause codes (V through Y codes) and health services codes (Z codes) as a part of the core classification.
• Significant discontinuities can be found in cause of death trends from the last year of ICD-9 use to the first year of ICD-10 use. In particular, decreases should be expected in deaths due to tuberculosis, viral hepatitis, lung cancer, acute myocardial infarction, and large decreases in pneumonia and accidental falls. Increases should be expected in HIV, septicaemia, breast and prostate cancers, diabetes, Parkinson's disease, cerebrovascular disease, alcoholic liver disease, renal failure, and Alzheimer's disease. Other areas such as suicide, colon cancer and SIDS show little change. For complete details see Statistics Canada's "Comparability of ICD-10 and ICD-9 for Mortality Statistics in Canada".1
• ICD-10-CA codes used for analyses on the Health Status Data website are grouped as follows:

REFERENCES AND RESOURCES

1. Statistics Canada. Comparability of ICD-10 and ICD-9 for Mortality Statistics in Canada. Ottawa: Ministry of Industry, 2005. Catalogue no. 84-548-XIE.
2. Anderson RN, Miniño AM, Hoyert DL, Rosenberg, HM. Comparability of Cause of Death Between ICD-9 and ICD-10: Preliminary Estimates. National Vital Statistics Report, Vol. 49, No. 2, May 18, 2001.
3. Canadian Institute for Health Information. Canadian Coding Standards For ICD-10-CA and CCI. Ottawa, ON: Canadian Institute for Health Information, 2003.
4. World Health Organization (WHO) International Classification of Diseases Online Version. 

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