SmartSteps: A Context-Aware, PrEP Adherence Intervention for Individuals With Substance Use Disorder

This study will develop a dataset of annotated smartphone usage in the context of PrEP adherence and nonadherence. In order to understand smartphone context, the investigators will utilize a digital pill system (DPS) to measure real-time PrEP ingestion events. Eligibility will be confirmed during the Screening Visit (Visit 1). During the Enrollment Visit (Visit 2), participants will complete a baseline quantitative assessment (e.g., sociodemographics, sexual history, attitudes about technology), receive training on the operation of the DPS and Beiwe, and will ingest their first digital pill dose under observation by study staff. Participants will be instructed to take one PrEP pill once daily while using the DPS and Beiwe app for 60 days. Participants will return for a study visit at the end of month one (Visit 3) for a refill of digital pills. Following a 24-hour period which no PrEP ingestion is detected by the DPS, participants will receive a brief online substance use and sexual risk survey, which will inform specific contexts of nonadherence. At the Month 1 Visit (Visit 3) and Month 2 Visit (Visit 4), timeline followback discussions will be conducted to better understand the context of any PrEP nonadherence events detected by the DPS, and phenotypic data collected by the Beiwe app, during the prior 30 days. At the Month 2 (Visit 4), the investigators will administer a blood draw for dried blood spot (DBS) testing to measure participants' PrEP adherence and compare it against adherence detected by the DPS. To gain insight into user experiences operating the DPS and Beiwe app as part of the study, the investigators will conduct the semi-structured qualitative exit interviews with participants at Month 2 (Visit 4).