Page 7: HIV and AIDS in Canada: Surveillance Report to December 31, 2014 - Methodology

Methodology

Data collection

This report presents data from four different sources relating to HIV and AIDS:

  • The National HIV/AIDS Surveillance System (Public Health Agency of Canada)
  • Immigration medical screening for HIV (Citizenship and Immigration Canada)
  • The Canadian Perinatal HIV Surveillance Program (CPHSP)
  • Vital Statistics - Death Database (Statistics Canada)

A description of each data source and its related strengths and weaknesses is provided below.

National HIV/AIDS Surveillance System (PHAC)

The National HIV/AIDS Surveillance System is a passive case-based surveillance system that collates data voluntarily submitted to PHAC from all provincial and territorial public health authorities. Provinces and territories provide the data through the National Case Reporting Form (Appendix 3) or through an electronic dataset transmission.

The data for HIV and AIDS are maintained in two unlinked databases. The HIV surveillance database consists of non-nominal data on people diagnosed with HIV infection including, but not limited to age, sex, race/ethnicity, country of birth, and risks associated with the transmission of HIV (exposure categories). Cases reported to PHAC must meet the national case definitionFootnote 3 which requires laboratory evidence of HIV infection through a confirmed, repeatedly reactive screening test for HIV antibody in a person over 15 months of age or for cases with history of non-maternal-fetal HIV transmission. The AIDS surveillance database captures non-nominal data on people diagnosed with AIDS (as per the national case definitionFootnote 4) and includes, in addition to the information included in the HIV surveillance database, the disease indicative of AIDS and vital status for the AIDS case (e.g., death).

Different HIV and AIDS reporting requirements and practices exist across the countryFootnote 5. Reporting of HIV diagnoses for individuals younger than two years of age varies between provinces and territories. For example, Quebec and Newfoundland and Labrador exclude positive serology results for HIV cases younger than two years of age. In most of the remaining provinces and territories where HIV infection in children younger than 18 months of age is confirmed using other testing modalities, HIV cases younger than two years of age are included within the surveillance data.

The completeness of epidemiologic information collected and submitted to PHAC varies by jurisdiction. In particular, exposure category and race/ethnicity information is incomplete for many case reports. Most significantly, Quebec does not submit exposure category or race/ethnicity information for HIV cases to PHAC. However, Quebec does publish provincial reports that include information on exposure category and race/ethnicity. In Ontario, completeness of exposure category and race/ethnicity data for HIV cases has changed over time. Completeness increased significantly for data from 2009 onwards due to the inclusion of supplementary data collected through the Ontario's Laboratory Enhancement Program (LEP). Manitoba does not provide disaggregated data on Aboriginal populations.

With respect to AIDS reporting, the following changes have occurred over time which affect the completeness of AIDS surveillance data:

  • Ontario: Data on exposure category, race/ethnicity and mortality are not available after 2004 due to changes in the reporting of AIDS cases.
  • Quebec: AIDS data (including mortality data) have not been available since June 30, 2003.
  • Newfoundland and Labrador: AIDS is no longer a reportable disease as of 2009.
  • Prince Edward Island: AIDS is no longer a reportable disease as of 2012.

Differences in the data published in this report and the data published in provincial and territorial surveillance reports may be due to reporting delays or differences in the date the data were extracted from the provincial and territorial surveillance databases. Where such differences are noted, it is recommended that data from the provincial and territorial reports be used. Appendix 1 contains a list of provincial and territorial data source programs.

The data presented in this surveillance report represent HIV and AIDS cases diagnosed on or before December 31, 2014 that were submitted by provincial and territorial surveillance programs to PHAC between March 15 and June 22, 2015 and extracted from the national surveillance database on June 25, 2015. Standardized data recoding procedures were applied to all submitted provincial and territorial datasets to create a national dataset for analysis.

Immigration medical screening for HIV (CIC)

CIC collects data relating to HIV during the immigration process. All foreign nationals applying for permanent residence and some applying for temporary residence must undergo an immigration medical examination (IME) either in Canada or overseas. On January 15, 2002, CIC added mandatory routine HIV screening to the IME for all applicants 15 years of age and older, as well as for applicants under the age of 15 who have certain risk factorsFootnote 6. CIC provides PHAC with non-nominal data (on immigrants diagnosed with HIV) collected during the IME process, including demographic information (e.g., sex, age, place of birth), as well as the year tested (for those tested in Canada) or the year the applicant landed in Canada (for those tested overseas).

Data relating to HIV and immigration were obtained from three sources for this surveillance report:

  • The CIC's database on HIV in June 2013 for all applicants screened in Canada or overseas who tested positive for HIV, including those who tested positive but did not land in Canada.
  • The CIC HIV database in March 2013 regarding HIV cases screened in Canada.
  • The CIC Health Branch Post-Arrival Health Public Health Liaison Unit Provincial Notifications - Overseas Notifications database on January 9, 2013 for HIV cases screened overseas and those who landed in Canada.

Canadian Perinatal HIV Surveillance Program

National data on the HIV status of infants exposed perinatally to HIV infection are collected through the CPHSP, an initiative of the Canadian Pediatric AIDS Research Group (CPARG). Support for the CPHSP is provided by the Canadian HIV Trials Network (CTN) and the Surveillance and Epidemiology Division within PHAC.

The CPHSP is a sentinel-based surveillance system that collects data on all identified infants and children in Canada born to mothers who are known to be infected with HIVFootnote 7. The CPHSP includes infants identified as exposed to HIV during pregnancy, older infants and children not identified in the perinatal period and those born outside Canada who are receiving care for HIV infection. Data were obtained through a national, non-nominal, confidential survey of infants known to participating pediatricians in tertiary care centres and specialists in HIV clinics across Canada. The HIV status of infants is reported as "confirmed infected," "confirmed not infected," or "infection status not confirmed," according to the United States Centers for Disease Control and Prevention (CDC) surveillance case definitions for HIV infectionFootnote 8. Tests for HIV deoxyribonucleic acid (DNA) or ribonucleic acid (RNA) (polymerase chain reaction) are used to confirm infection status by four months of age. Infants are classified as "not confirmed" if they have not yet received the required number of tests to determine their HIV status. The current status of confirmed infected infants is defined as "asymptomatic," "symptomatic," "died of AIDS," "died of a cause other than AIDS" or "lost to follow-up".

The data presented in this surveillance report were extracted from the CPHSP's database in March 2015 and provided to PHAC.

Vital Statistics Death Database (SC)

Under a federal/provincial/territorial agreement, all deaths, regardless of cause must be registered with the provincial and territorial registrars of the offices of vital statisticsFootnote 9. The central registry in each province and territory provides data from death registration forms to the Health Statistics Division of Statistics Canada, which maintains the Death Database, a cumulative record of death statistics. Information on cause of death is coded using the International Classification of Diseases (ICD).

The 9th revision (ICD-9) is used for deaths that occurred between 1979 and 1999; codes 042-044 include deaths attributed to HIV infection. The 10th revision (ICD-10) is used for deaths that occurred from 2000 onward; codes B20-B24 include deaths attributed to HIV infection. Data are not comparable between the two coding systems because of changes in coding definitions.

From 1987 to 1999, data on mortality due to HIV infection were obtained using the Data Extraction and Analysis (DEXA) system (extracted in August 2014). DEXA is a web-enabled SAS-based application that facilitates access to centralized data holdings in PHAC, which include vital statistics from Statistics Canada. Data from 2000 to 2011 were obtained from the Death Database, Health Statistics Division, Statistics Canada (extracted in August 2014).

Tabulation and presentation of data

Key findings are summarised in the At a glance section of this report. In addition, the following series of detailed data tables are presented in Sections I to VI:

Section I:
HIV in Canada: Reported HIV cases to December 31, 2014
Section II:
Immigration medical screening for HIV
Section III:
Report of the Canadian Perinatal HIV Surveillance Program: 1984-2014
Section IV:
AIDS in Canada: Reported AIDS cases to December 31, 2014
Section V:
Mortality due to HIV and AIDS in Canada: Vital statistics from 1987 to December 31, 2011
Section VI:
International Statistics on HIV and AIDS

No statistical procedures were used for comparative analyses in this report. Nor were any statistical techniques applied to account for missing data. Data in tables with small cell sizes (n ≤ 5) were reviewed for possible issues regarding data quality and case identification. Strategies such as data suppression or collapsing data categories were used if deemed necessary by national analysts or by provincial or territorial data providers.

This report also includes the following appendices:

Appendix 1:
Data contributors
Appendix 2:
Exposure category hierarchy
Appendix 3:
HIV/AIDS Case Report Form
Appendix 4:
List of HIV-endemic countries
Appendix 5:
Data limitations
Appendix 6:
Terminology

Footnotes

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