The objective of the linkage project is to increase the analytical and research value of the individual CIHI files by including information about deaths that occur after discharge from hospital. To that end, the linked dataset will be used to develop and validate health care indicators and performance measures as well as perform survival and outcome analyses on acute inpatient data while considering such elements as efficiency, continuum of care, outcomes and disparities in health and longevity.
To achieve this objective, the patient records in the Discharge Abstract Database (DAD), the National Ambulatory Care Reporting System (NACRS) and the Ontario Mental Health Reporting System (OMHRS) were linked to the CVSD. In addition to the deaths occurring in hospitals which are captured in the CIHI datasets, the linked file will provide information on patients who have died following their discharge from an acute care hospital or an emergency room. Statistics Canada does not have Quebec hospitalization data (RAMQ) as part of its data holdings and thus hospitalizations that occurred in the province of Quebec are not included in the linked datasets.
The Data
Discharge Abstract Database
The DAD includes administrative, clinical and demographic information on hospital discharges (including in-hospital deaths, sign-outs and transfers) from all provinces and territories, except Quebec. Over time, the DAD has also been used to capture data on day surgery, long-term care, rehabilitation and other types of care. DAD data for fiscal years 2000/2001 to 2022/2023 were included in the linkage.
In the DAD, jurisdiction-specific instructions for collection of data elements evolve over time. Collection of each data element may be mandatory, mandatory if applicable, optional or not applicable. Collection requirements can vary by jurisdiction and by data year. Researchers will find the listings of DAD data elements under the heading "Data Elements" at the DAD Metadata website. The documents on the website include information on mandatory versus optional collection status for each data element by jurisdiction, which is key to understanding coverage of data elements in the DAD. Please note that DAD data elements that could present an increased risk of direct or indirect identification of an individual were excluded in the DAD analytical file for this record linkage project.
National Ambulatory Care Reporting System (NACRS)
The NACRS contains data for hospital-based and community-based ambulatory care including day surgery, outpatient and community-based clinics, and emergency departments. Client visit data is collected at time of service in participating facilities from several jurisdictions. NACRS data for fiscal years 2002/2003 to 2022/2023 were included in the linkage.
For details on the provincial data coverage, please refer to the Data Quality Documentation, available under the "Data Quality" section of the NACRS Metadata website.
In NACRS, jurisdiction-specific instructions for collection of data elements evolve over time. Similar to DAD, collection of each data element may be mandatory, mandatory if applicable, optional or not applicable. Collection requirements can vary by jurisdiction and by data year.
Researchers will find the listings of NACRS data elements under the "Data Elements" section of the NACRS Metadata website. The documents on the website include information on mandatory versus optional collection status for each data element by jurisdiction, which is key to understanding coverage of data elements in NACRS.
Ontario Mental Health Reporting System (OMHRS)
The Ontario Mental Health Reporting System (OMHRS) analyzes and reports on information submitted to CIHI about all individuals receiving adult mental health services in Ontario, as well as some individuals receiving services in youth inpatient beds and selected facilities in other provinces. OMHRS includes information about mental and physical health, social supports and service use, as well as care planning, outcome measurement, quality improvement and case-mix funding applications. OMHRS data for fiscal years 2005/2006 to 2022/2023 were included in the linkage.
In OMHRS, instructions for collection of data elements for each assessment type evolved over time. Collection of each data element may be mandatory, optional, optional depending on an associated data element, or not applicable. Researchers will find the listings of OMHRS data elements under the heading "Data Elements" at the OMHRS Metadata website. The documents on the website include information on mandatory versus optional collection status for each data element by type of assessment, which is key to understanding coverage of data elements in OMHRS.
Canadian Vital Statistics Death Database (CVSD)
The Canadian Vital Statistics Death Database (CVSD) is a census of all deaths occurring in Canada each year. Deaths are reported by the provincial and territorial Vital Statistics Registries to Statistics Canada; the information provided includes demographic and cause of death information. Cause-of-death information is coded using the version of the International Classification of Diseases (ICD) in effect at the time of death. Records eligible for record linkage were deaths that occurred from January 1, 2000 through December 31, 2022.
In addition to the variables from the CVSD, the file includes variables from the Postal Code Conversion File+ (PCCF+) for each linked record. The PCCF+ was generated using the CVSD variable DEA_Q150 (usual residence of the deceased: postal code).
File structure, layout
Separate output files, one for each cohort by fiscal year are available for analytical use. The cohort files (DAD, NACRS, and OMHRS) include all the records from the cohort (linked and unlinked). The variable required to merge the output files is STC_ID.
The STC_ID identifies unique individuals and allows those individuals with multiple transactions within a dataset or across cohort datasets to be identified. The STC_ID allows records to be merged across datasets (e.g., DAD to NACRS, for example) so that a larger picture of health interventions for an individual can be analysed. Names and other personal identifiers are not included on the file.
Researchers can choose to use the outcome files as event-based (each row of data represents a hospitalization) or person-based (each row of data represents an individual). In order to use a file as a person-based file, the researcher must transform the data to include all hospital information for one person as one record (one row on the data file).