International Classification of Diseases, Tenth Revision (ICD-10)

• The International Classification of Diseases (ICD) is used to classify diseases and other health problems recorded on many types of health and vital records including death certificates and hospital records. ICD-10 was endorsed by the Forty-third World Health Assembly in May 1990 and came into use in WHO Member States starting in 1994.
• ICD-10 was implemented with mortality data in Ontario on January 1, 2000.
• ICD-9 contained 17 chapters plus two supplementary classifications: the Supplementary Classification of External Causes of Injury and Poisoning (the E code) and the Supplementary Classification of Factors Influencing Health Status and Contact with Health Services (the V code). In ICD-10 these are no longer considered to be supplementary and were included as a part of the core classification. Also in ICD-10 chapters have been added and rearranged. Chapter titles for ICD-9 and ICD-10 are shown in the table below. ICD-10 contains 21 chapters.
• ICD-10-CA was implemented with hospitalization data in Ontario on April 1, 2001. CIHI is responsible for maintaining and updating ICD-10-CA every two years. This is to ensure the continued relevancy and utility of ICD-10-CA and to reflect Canadian practice patterns. ICD-10-CA includes the addition of fifth and sixth characters to provide added specificity. ICD-10-CA also includes two additional chapters in the tabular list. The Morphology of neoplasms is incorporated as Chapter XXII. Chapter XXIII captures provisional codes for research and temporary assignment. On rare occasions codes in ICD-10 and ICD-10-CA differ slightly such as for 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.
• ICD-10 is far more detailed than ICD-9 with about 8,000 categories in ICD-10 compared to approximately 5,000 in ICD-9.
• ICD-10 uses alphanumeric codes whereas ICD-9 used numeric codes.
• 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 large increases in 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" (see reference below).
• ICD-10 provides less detail than ICD-9 for some causes. For example the ICD-10 code V86 includes but is not specific to snowmobile accidents whereas there was a specific ICD-9 code for this. However, ICD-10-CA does add a fifth digit to specify accidents involving snowmobiles. For the majority of causes, ICD-10 provides greater detail than ICD-9 did.

ICD Chapters

References and Resources

1. 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. URL: http://www.cdc.gov/nchs/data/nvsr/nvsr49/nvsr49_02.pdf. Final estimates available at URL: ftp://ftp.cdc.gov/pub/Health_Statistics/NCHS/Datasets/Comparability/icd9_icd10/
2. Canadian Institute for Health Information. Canadian Coding Standards For ICD-10-CA and CCI. Ottawa, ON: Canadian Institute for Health Information, 2003.
3. World Health Organization (WHO) International Classification of Diseases Online Version. URL: http://www.who.int/classifications/icd/en/
4. Statistics Canada. Comparability of ICD-10 and ICD-9 for Mortality Statistics in Canada. Ottawa: Ministry of Industry, 2005. Catalogue no. 84-548-XIE. URL: http://www.statcan.ca/english/freepub/84-548-XIE/84-548-XIE2005001.htm