Technical Notes: Data sources
Where do these data come from?
- Data on this website come from the Public Health Ontario (PHO) Laboratory, which conducts centralized HIV diagnostic testing for the province. Data on the annual number of pregnant people in Ontario (used to calculate the estimated percent of pregnant people who received a prenatal HIV test) was provided by the Better Outcomes Registry & Network (BORN).
- When someone is tested for HIV in Ontario, the health care provider conducting the test (e.g. a physician, nurse or HIV counselor) fills out an HIV test requisition form that is sent to PHO. The requisition collects information on the individual being tested for HIV, including their age, sex, geographic location and HIV risk factors.
- When a test is HIV-positive, a Laboratory Enhancement Program (LEP) form is sent to the health care provider who conducted the test to collect more information on the individual tested. LEP data in this report is only used to determine which positive HIV tests were from individuals with previous evidence of HIV so that they can be properly categorized. Since 2009, the LEP form has collected information on race/ethnicity, country of birth, and test history (data not historically collected on the HIV test requisition, but collected starting in 2018).
- In February 2018, PHO implemented a revised HIV test requisition that collects additional information on transgender identity, race/ethnicity, and country of birth. OHESI now reports HIV test data on transgender identity and race/ethnicity from the subset of HIV tests that were submitted using the new requisition form.
- With rapid/point-of-care (POC) tests, an HIV test requisition form is completed and submitted to PHO with a sticker attached indicating the result of the POC test. POC tests are included in the total numbers of HIV tests, and reactive POC tests with confirmatory laboratory tests are included as positive HIV tests in the HIV test positivity rates if they do not have previous evidence of HIV.
- Prenatal HIV tests are part of an ongoing HIV testing program offered to all pregnant individuals as part of their prenatal care. Prenatal HIV testing results are reported separately. They are not included in the number of HIV tests or population testing rates. However, to calculate HIV test positivity rates, HIV-positive prenatal tests are included in the numerator while HIV-negative prenatal tests are not included in the denominator. From 2012 to 2019, the annual number of HIV-positive prenatal tests ranged from 2 to 10 (where no previous evidence of HIV infection was known).
What are some of the strengths of these data and our approach to presenting it?
- The vast majority of HIV diagnostic testing conducted by health care providers in Ontario is done by PHO and therefore included.
- Age and sex data on the test requisition are very complete and available for more than 96% of HIV tests since 2010. Approximately 17% of diagnoses are missing information on address of residence in 2019 and assigned based on provider address, leaving 0.02% of tests with unknown health region.
What are some of the limitations of the data?
- The HIV response in Ontario focuses on priority populations or populations most affected by HIV, which are a combination of risk factors (e.g. men having sex with men, injection drug use), country of birth, and race/ethnicity (e.g. White, Black). As information on race/ethnicity and country of birth was not available on test requisition forms until early 2018, we are unable to report on HIV test data by priority populations. HIV diagnosis data is reported by priority populations, however the information required to assign the status of each of the priority populations is not reported for varying proportions of first-time HIV diagnoses between 2010 and 2019: GBMSM 14.8%; ACB 28.5%; PWID 30.2%; Indigenous Peoples 32.2%; Women <1%.
- Risk factor information is not reported or indicated as “none” on approximately two thirds of HIV test requisition forms.
- Information about risk factors and demographics are only available when test forms are filled out completely and correctly. HIV test requisitions are not filled out completely for all new HIV diagnoses. Furthermore, approximately 37% of LEP forms are not returned by 3 months and in total, approximately 31% of LEP forms in 2019 were not returned. After combining information from both forms (HIV test requisition and LEP), exposure category information is missing for approximately 27% of positive HIV tests in 2019.
- Due to race/ethnicity historically (prior to 2018) only been collected on the LEP and not the HIV test requisition, and low uptake of the new test requisition form that does collect information on race/ethnicity since 2018, there is a high rate of race/ethnicity information that is missing; approximately 31% of positive HIV tests in 2019.
- It is unknown whether some categories or populations may be more likely to be missing information, which could potentially bias the proportions. There may also be bias due to varied practices among providers for filling out the requisition and LEP forms. For example, some providers may ask about ethnicity or risk factors, while others may not ask or make assumptions.
- The time it takes for LEP forms to be returned can result in reporting delays.
- HIV tests are reported as a rate per 1,000 people. It is possible that an individual may test more than once per year and, therefore, the number of unique individuals tested may be lower than the total number of tests. Also, males may be more likely than females to test more than once in a given year.
- Data on transgender identity and race/ethnicity are reported from a subset of the total HIV tests where the new requisition was used. HIV tests using this new requisition comprised approximately one third of all HIV tests in 2019. Due to this low uptake with the new requisition thus far, these findings may not be representative of all HIV tests in Ontario in 2019.
- Data on transgender individuals has not been collected in a consistent manner over time. For this reason, transgender individuals are not included in any of the HIV diagnosis counts or rates when stratified by sex. Transgender females are counted when reporting on Women and transgender males are counted as GBMSM if sex with a man is reported. As data collection becomes more consistent with capturing transgender identity, future reports will incorportate this information.
Please refer to each respective report for more specific information pertaining to the data used, and its strengths and limitations.