Administrative lost to follow-up
An individual in the Ontario HIV Laboratory Cohort is considered to be a person with diagnosed HIV who is living in Ontario until administratively lost to follow-up, defined as having had no viral load test for more than two consecutive years and no viral load test in later years. Individuals lost to follow-up are assumed to have died or migrated out of the province, and are removed from the cohort. Based on the constraints of this definition, a diagnosed individual who is actually living in Ontario would be removed from the cohort if they haven’t had a VL test in more than two years. If this individual goes on to have a viral load test in the future, they are re-entered into the cohort. In additional analyses, the lost to follow-up criteria is increased to three years.
Anonymous HIV testing
A type of non-nominal HIV diagnostic testing where no identifying information on the individual being tested is collected on the test requisition form. The lack of identifying information means that it is not possible to link anonymous HIV-positive diagnostic tests to viral load tests within the HIV Datamart.
Coded HIV testing
A type of non-nominal HIV diagnostic testing where a code, instead of the name of the individual being tested, is collected on the test requisition form. The lack of identifying information means that it is not possible to link coded HIV-positive diagnostic tests to viral load tests within the HIV Datamart.
An integrated data platform composed of Public Health Ontario Laboratory’s HIV diagnostic and viral load testing databases. Within the datamart, diagnostic and viral load test records are linked together for the same person (however, linkage is not possible for non-nominal HIV-positive diagnostic tests). More information on the datamart can be found here.
HIV-positive diagnostic test
Defined as a blood sample that has initially tested reactive on a screening test (either at the laboratory or on a point-of-care / rapid test), and has also tested HIV-positive on a second test at the laboratory (known as a confirmatory test). HIV-positive diagnostic tests in the HIV Datamart include people who were diagnosed with HIV for the first ever time in Ontario, as well as people who were diagnosed HIV-positive elsewhere and moved to Ontario and tested again.
Newly HIV diagnosed
Individuals in the HIV Datamart who received their first ever HIV-positive diagnosis in Ontario (i.e. were not diagnosed elsewhere and then moved to Ontario and tested again). Individuals are considered newly diagnosed in Ontario if they have record of a nominal HIV-positive diagnostic test and no evidence of being previously diagnosed (i.e. no detectable viral load test or CD4 count before their diagnosis date, first VL after diagnosis not suppressed).
Nominal HIV testing
A type of HIV diagnostic testing where the test requisition form contains the name of the individual being tested. Nominal HIV tests can be linked to viral load tests in the HIV Datamart using patient identifiers.
Non-nominal HIV testing
A type of HIV diagnostic testing where the test requisition form does not contain the name of the individual being tested. There are two types of non-nominal testing in Ontario: anonymous and coded. The lack of identifying information means that it is not possible to link non-nominal HIV-positive diagnostic tests to viral load tests within the HIV Datamart.
Ontario HIV Laboratory Cohort
A population-based, retrospective cohort of people with diagnosed HIV living in Ontario created using Public Health Ontario Laboratory’s HIV Datamart. It includes people in the datamart who have record of a nominal HIV-positive diagnostic test and/or at least 1 viral load test, and who have not been administratively lost to follow-up. In additional analyses, non-nominal HIV-positive diagnoses are also included in the cohort. More information on the cohort can be found here
Along with each HIV diagnostic and viral load test, a test requisition form is completed. It is filled out by the provider who conducted the test and collects information on the individual being tested. The viral load test requisition form collects information on whether the individual is on antiretroviral treatment at the time of testing and most recent CD4 cell count.