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about hospitalization data

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  • For each data source, information about data collection and analytical methods, limitations, the citation and additional resources can be found on the Data Sources and Methods page.


Original Source: Canadian Institute for Health Information (CIHI)
Cite as:Hospital In-Patient Discharges, 2003-2017, Canadian Institute for Health Information (CIHI). IntelliHEALTH Ontario, Ministry of Health and Long-Term Care.


Data Collection Methods

  • Prior to April 1, 2001, the International Classification of Diseases Ninth Revision (ICD-9) was used to classify hospitalization records. After this date, the International Statistical Classification of Diseases and Related Health Problems, Canada, Version 10, 2007 (ICD-10-CA) was used.
  • The “most responsible diagnosis” code gives the primary reason for the hospital stay and is coded using the ICD-10-CA (codes starting with the letters A through U).
  • A second set of codes for external causes (those starting with the letters V through Y) are used in the case of an injury to classify the environmental events, circumstances and conditions that caused the injury, for example motor vehicle traffic injury. External cause codes are the principal means of classifying injury deaths but are not used as a main problem for emergency department visits, so they need to be examined separately.
  • The ICD-10-CA codes used for analyses on the Health Status Data website can be accessed here.

Data Analysis Methods

  • The counts presented on the Health Status Data website represent the number of distinct discharges and not the number of distinct individuals, as an individual may have multiple discharges during the time period examined.
  • Data are collected based on location of hospital but are generally analyzed by the residence of the patient for health status purposes.
  • ICD-10-CA Chapter 15: Pregnancy, Childbirth and the Puerperium and Chapter 21: Factors influencing health status and contacts with health services were excluded from analysis.
  • The most responsible diagnoses are grouped into categories based on ICD-9 or ICD-10 coding. A mutually exclusive sub-set of these groupings are defined as “leading causes of hospitalization”, which represent specific diseases or conditions of public health interest. ICD groupings which include all residual codes within a chapter not elsewhere classified are not presented on the Health Status Data website as leading causes of hospitalization. Therefore, the leading causes of hospitalization include only a selected list of specific diseases or conditions. The ICD-10-CA codes used for these analyses can be accessed here.
  • Within the leading cause of hospitalization, most responsible diagnoses related to injuries were coded based on Chapter 19 (S & T codes). In contrast, the leading causes of injuries are defined based on the external cause codes. Since multiple external cause codes can be assigned for each hospitalization record, the count within the leading causes of injuries will be higher than the count of injuries within the leading causes of hospitalizations.
  • Hospitalization rates are calculated using crude and age-standardization methods. Age-standardized rates are calculated using the direct method of standardization with the 2011 Canadian population as the standard population.


  • Co-morbidity contributes uncertainty to classifying the most responsible diagnosis.
  • Hospitalization data provide only a crude measure of the condition being quantified since a person may not be hospitalized, may be hospitalized several times for the same disease or injury event, or discharged from more than one hospital (when transferred) for the same disease or injury event.
  • Data are influenced by factors that are unrelated to health status such as availability and accessibility of care, and administrative policies and procedures. This may influence comparisons between areas and over time.
  • Ontario residents treated outside of the province are excluded.
  • Effective April 1, 2006, hospitalizations for adults occupying designated mental health beds are collected in the Ontario Mental Health Reporting System (OHMRS). This change will result in a reduction of hospitalizations captured in the hospital separation data, under Chapter 5: Mental and Behavioural Disorders.


  1. Association of Public Health Epidemiologists in Ontario – Hospitalization Data

Last updated: June 21, 2019

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