Figure 2.

Historical trends and estimated British Columbia Ministry of Health Seek and Treat for Optimal Prevention of human immunodeficiency virus/AIDS intervention effects for highly active antiretroviral treatment (ART) initiation and retention initiatives. The observed monthly probability of ART initiation among diagnosed people who inject drugs (PWID; panel A) and non-PWID (panel B) for British Columbia from 1996–2010 was used to generate counterfactual ART initiation probabilities approximating the status quo (ie, no additional public health investments to support ART initiation) for the intervention period (dashed line). ART initiation probabilities in Vancouver Coastal Health Authority, observed in linked individual-level data, were used to determine the intervention effect. The same procedure was used to determine probabilities of ART reentry (panels C and D). To adequately capture changes in the probability of ART dropout within the dynamic simulation model, we extrapolated counterfactual CD4-based transition probabilities using multistate Markov models for PWID and non-PWID (panels E and F) and estimated observed dropout probabilities during the intervention period using similar procedures as described above. Abbreviations: ART, highly active antiretroviral treatment; PWID, people who inject drugs.