DISCUSSION
RECRUITMENT
The population in this study included ED patients with SUD. Retention at the three-month follow-up was 89% and remained above 80% for subsequent follow-ups. Site selection based on predetermined criteria, inclusion and exclusion criteria that included criteria that increased the likelihood of successful follow-up with participants, adequate compensation for study visits, ongoing training and monitoring of recruitment and retention efforts, effective use of technology (eg, tablet computers), and flexibility in enrollment and conducting follow-up assessments were factors considered to support successful recruitment and retention of participants. Urban sites with a large ED census of patients and availability of substance use treatment programs were also key factors in site selection for this study (We chose certain inclusion and exclusion criteria to support successful follow-up with participants (Staff flexibility at enrollment (eg, meeting patients when they felt well enough to complete assessments and were not busy with medical care) and follow-up (eg, completing follow-ups by phone or in the community and when convenient to the participant), was the single most likely factor to have mediated the success in recruitment and retention. We did not gather data on the participant’s opinion of using tablet computers, but it is hoped that this minimized any feelings of embarrassment or perceived stigmatization in reporting sensitive drug use information. Similarly, compensation is presumed to have been acceptable as there were no complaints about compensation being too little or too much over the course of the study.The average number of contact attempts was 26 and ranged up to 70 to reach a participant for a follow-up visit. Most commonly, participants or their locators were reached by phone or via letters sent, but conducting online searches and using social media (ie, Facebook) to connect with participants were important access points as well. Both the amount of time and effort this intense level of follow-up entailed and the potential for participants to feel harassed or coerced to participate must be seriously considered. To ensure participants do not feel harassed or coerced, it is important to emphasize that participation is voluntary. Additionally, documentation of contact attempts ensures that participants who have refused to participate are not contacted again and contact methods that have been unsuccessful are not repeated. The level of effort to contact participants is time-consuming, and it is important to appropriately plan for this. Likewise, thoughtful and strategic outreach to enrolled patients requires careful internal documentation and communication within the follow-up team, also requiring time and effort.For future research in EDs we would recommend using wireless internet data cards rather than relying on wireless connections to the ED network. Losing internet connection became a point of frustration for both participants and enrollment study staff conducting interviews as they would sometimes lose data and be forced to repeat parts of the baseline assessment. A wireless internet data card allows users to access online information anytime and anywhere without getting disconnected from the network.Obtaining participant consent upfront for texting, emailing, and searching for participants through publicly available data including social media networks such as Facebook is recommended. We implemented this midway through the study, and some study sites had difficulty in gaining permission from their IRBs to use these resources without participant consent. We would also recommend seeking IRB approval and participant consent to continue working with enrolled study participants who might become incarcerated during the study.