CANADIAN CHRONIC DISEASE SURVEILLANCE SYSTEM:
SUMMARY OF METHODS
The Canadian Chronic Disease Surveillance System (CCDSS) is a collaborative network of provincial and territorial surveillance systems supported by the Public Health Agency of Canada (PHAC).
In each province and territory, the health insurance registry database is linked to the physician billing and hospitalization databases using the health card number as a unique personal identifier. Where available and specified by the case definition, data from prescription drug databases are also linked.
Case definitions are applied to these linked databases to identify individuals with chronic diseases and aggregate data are sent to PHAC. The aggregate data are used by PHAC to estimate the incidence, prevalence, all-cause mortality, use of health services (e.g. hospitalizations and physician visits), and comorbidities on a national level.
While data are collected since 1995–1996 in most provinces and territories, the start year for reporting is determined on a disease by disease basis to not only allow enough time to capture all prevalent cases but to ensure previously prevalent cases are excluded from incident cases.
In the latest edition of the CCDSS Data Tool, data up to 2015–2016 are reported for the following chronic diseases with the exception of juvenile idiopathic arthritis, where data up to 2013–2014 are reported:
- heart failure
- ischemic heart disease
- acute myocardial infarction
- hospitalized stroke events
Chronic respiratory diseases
- chronic obstructive pulmonary disease
Mental illness (use of health services)
- mental illness
- mood and anxiety disorders
- hip fractures
- gout and crystal arthropathies
- rheumatoid arthritis
- juvenile idiopathic arthritis
- dementia, including Alzheimer’s disease
- multiple sclerosis
- parkinsonism, including Parkinson’s disease
DEFINITIONS OF TERMS
Age-Specific Rates: Incidence, prevalence and all-cause mortality rates calculated for a specific age group using randomly rounded counts.
Age-Standardized Rates: Incidence, prevalence and all-cause mortality rates age-standardized to the 2011 Canadian population, using raw counts and life-course age groups, in order to adjust for differences in population age structure.
Case Definition: CCDSS disease specific case definitions are applied to identify individuals with the disease (cases). Refer to the accompanying case definition documentation for the disease specific criteria used, including the 9th or 10th edition of the International Classification of Disease (ICD), Canadian Classification of Health Interventions (CCI) and Canadian Classification of Diagnostic, Therapeutic and Surgical Procedures (CCP) codes.
Confidence Interval: The 95% confidence interval shows an estimated range of values which is likely to include the true value 19 times out of 20.
Crude Rates: Incidence, prevalence and all-cause mortality crude rates calculated using randomly rounded counts.
Incidence Rate: The rate of new cases occurring during the specified fiscal year among individuals with valid health insurance coverage who were not already a prevalent case during the same fiscal year (April 1 – March 31).
Mortality (All-Cause) Rate: The rate of death from any cause among individuals with and without the disease during the capture period (April 1, 1995–1996 to March 31 of the specified year) among those with valid health insurance coverage.
Mortality (All-Cause) Rate Ratio: The all-cause mortality rate among individuals with the disease divided by the all-cause mortality rate among individuals without the disease among individuals with valid health insurance coverage. A rate ratio greater than one indicates that individuals with the disease experience a higher mortality burden compared to individuals without, regardless of the cause of death. Assuming the baseline age-standardized mortality rates between those with and without the disease are similar, the difference in their all-cause mortality represented by the rate ratio can be attributed to deaths directly or indirectly related to the disease.
Prevalence Rate: The proportion of cases among individuals with valid health insurance coverage during the specified capture period (April 1, 1995–1996 to March 31 of the specified year). In the CCDSS Data Tool, two different types of period prevalence are reported: annual and cumulative. A single year of data is used to calculate annual prevalence, while all available years of data are used to determine cumulative prevalence. In addition, active prevalence is reported, which represents a subset of cumulative prevalence, i.e. those meeting the active prevalence criteria.
Before rates were calculated the following data procedures were applied:
Age Group Aggregation: All provincial/territorial age groups have been aggregated using the following life-course age groups: 1-19, 20-34, 35-49, 50-64, 65-79 and 80+ with a few exceptions:
- For parkinsonism including Parkinson’s disease, osteoporosis, hip fractures and heart failure the first age group is 40-49;
- For rheumatoid arthritis, the first age group is 16-34; and
- For juvenile idiopathic arthritis, only one age group was used, i.e. 0-15.
Suppression: Rates and rate ratios are not reported when the counts were less than 10 or the coefficient of variation of the rate was greater than 33%.
Random Rounding: All provincial/territorial and Canadian counts 10 or greater were randomly rounded up or down to the nearest 10. Random rounding is only used to calculate crude rates. Age-standardized rates are based on non-rounded counts.
FORMULAE USED FOR CALCULATION OF PREVALENCE, INCIDENCE AND ALL-CAUSE MORTALITY
- Annual = (Total number of individuals meeting annual case criterion during the capture period / Total number of individuals with valid health insurance during the fiscal year) * 100 or 100,000 for hip fractures and hospitalized stroke events.
- Cumulative = (Total number of individuals with a case date during the capture period / Total number of individuals with valid health insurance during the fiscal year) * 100.
- Active Prevalence = (Total number of cumulative prevalence cases meeting active case criteria during the capture period / Total number of individuals with valid health insurance during the fiscal year) * 100.
Incidence Rate = [Total number of incident cases / (Total number of individuals with valid health insurance during the fiscal year - prevalent cases at the beginning of the fiscal year)] * 100,000.
Mortality (All-Cause) Rates and Rate Ratio
- Mortality (All-Cause) Rate With the Disease = (Total number of individuals with the disease who died of any cause in the specified fiscal year / Total number of people with the disease at any time during the capture period)* 100,000 or 1,000 for hip fracture.
- Mortality (All-Cause) Rate Without the Disease = (Total number of individuals without the disease who died of any cause in the specified fiscal year / Total number of people without the disease at any time during the capture period)*100,000.
- Rate Ratio of (Age-Standardized) Mortality (All-Cause) Rates = [(age-standardized) mortality rate with the disease)] / [(age-standardized mortality rate without the disease)].
PROVINCIAL AND TERRITORIAL NOTES
Newfoundland and Labrador: Census-based population estimates were used to report rates before 2008–2009.
Nunavut: Counts and rates for data before 2005–2006 were excluded because Community Health Centre data were not available.
Quebec: Data were not available for 1995–1996.
Saskatchewan: Data were not available for 2015–2016.
Yukon: Data were not available.
Note: All disease-specific notes, including provincial/territorial specifications, are included in the CCDSS Case Definitions documentation:
CCDSS Case Definitions
These data were made possible through collaboration between PHAC and the respective provincial and territorial governments of British Columbia, Alberta, Saskatchewan, Manitoba, Ontario, Quebec, New Brunswick, Nova Scotia, Prince Edward Island, Newfoundland and Labrador, Northwest Territories, and Nunavut. No endorsement by the provinces and territories is intended or should be inferred. Provincial and territorial data were contributed to the CCDSS as of April 2017 (data up 2013–2014) and as of May 2018 (data up to 2015–2016).