Why look at patterns in engagement in care, antiretroviral treatment and viral suppression?
- To maintain and improve health and reduce the risk of new HIV transmissions, it is important for people living with HIV to be diagnosed, in care, on antiretroviral treatment (ART), and virally suppressed (see HIV prevention, engagement and care cascade).
- Understanding cascade trends can help measure the impact of HIV care and monitor progress toward meeting the UNAIDS 90-90-90 targets.
- Identifying gaps in the cascade can help the care system prioritize interventions and inform program/policy changes to improve engagement.
- Although being in care, on ART, and virally suppressed are important for health and well-being, they do not necessarily reflect overall quality of life for a person living with HIV.
Where do these data come from?
- Data in this section comes from the Public Health Ontario Laboratory (PHOL), which conducts centralized HIV diagnostic and viral load (VL) testing for the province.
- PHOL’s HIV diagnostic and VL databases were combined and used to create a group (also known as a cohort) of people living with diagnosed HIV in Ontario – referred to as the Ontario HIV Laboratory Cohort – whose cascade engagement can be monitored over time. The cohort includes all people in the laboratory databases who have record of a nominal HIV-positive diagnostic test and/or at least one VL test, and have not been administratively lost-to-follow-up (LTFU). For more information on who is and isn’t included in this cohort, go here.
- All information in the PHOL databases is confidential, and only de-identified aggregate data are shared with OHESI partners.
What are some of the limitations of these data?
- If a person in the cohort does not have a VL test in a given year, they are assumed to be not on ART for that year, which may underestimate the number on ART.
- When a person receives a VL test, a provider fills out a test requisition form and sends it to the laboratory along with a blood sample for testing. The VL test form records information on whether the person getting tested is on ART. However, this information is missing for about 17 to 20% of VL tests each year. To reduce the impact of this missing data, conservative assumptions on ART status are made for requisitions with missing information. To calculate the percent of diagnosed individuals who are on ART, individuals with missing treatment information are assumed to be on ART if they have a suppressed VL, while unsuppressed individuals with missing treatment data are assumed to be off ART (note: a different assumption is made to calculate the percent of people on ART who are virally suppressed – see “Virally suppressed” section). Since some unsuppressed individuals with missing treatment information may actually be on treatment, the number on ART is likely underestimated.
- While the Ontario HIV Laboratory Cohort represents our best province-wide understanding of the cascade among diagnosed people with HIV in Ontario, it is unclear to what extent the cohort represents all people with an HIV-positive diagnosis who are currently living in the province. Representativeness may be limited by the exclusion of non-nominal HIV-positive diagnostic tests (although individuals diagnosed non-nominally are included in the cohort when they receive a VL test) and the inability to directly account for deaths and migration out of the province. More information on these limitations can be found here.