The cascade of HIV care in British Columbia, Canada, 1996-2011: a population-based retrospective cohort study

Background The cascade of HIV care has become a focal point for implementation efforts to maximise the individual and public health benefits of antiretroviral therapy. We aimed to characterise longitudinal changes in engagement with the cascade of HIV care in British Columbia, Canada, from 1996 to 2011. Methods We used estimates of provincial HIV prevalence from the Public Health Agency of Canada and linked provincial population-level data to define, longitudinally, the numbers of individuals in each of the eight stages of the cascade of HIV care (HIV infected, diagnosed, linked to HIV care, retained in HIV care, highly active antiretroviral therapy (HAART) indicated, on HAART, adherent to HAART, and virologically suppressed) in British Columbia from 1996 to 2011. We used sensitivity analyses to determine the sensitivity of cascade-stage counts to variations in their definitions. Findings 13140 people were dassified as diagnosed with HIV/AIDS in British Columbia during the study period. We noted substantial improvements over time in the proportions of individuals at each stage of the cascade of care. Based on prevalence estimates, the proportion of unidentified HIV-positive individuals decreased from 49.0% (estimated range 36.2-57.5%) in 1996 to 29.0% (11.6-40.7%) in 2011, and the proportion of HIV-positive people with viral suppression reached 34-6% (29.0-43.1%) in 2011. Interpretation Careful mapping of the cascade of care is crucial to understanding what further efforts are needed to maximise the beneficial effects of available interventions and so inform efforts to contain the spread of HIV/AIDS.