BACKGROUND
Web-based respondent-driven sampling (webRDS) is a novel sampling method for the recruitment of participants for generating population estimates, studying social network characteristics and delivering health interventions. However, the application, barriers and facilitators, and recruitment performance of webRDS have not yet been systematically investigated.
OBJECTIVE
Our objectives were to provide an overview of published research using webRDS, and to investigate factors related to webRDS recruitment performance.
METHODS
We conducted a scoping review on webRDS studies published between 2000 and 2019. We used Moore et al.’s (2015) ‘process evaluation of complex interventions framework’ to gain insights into how webRDS was implemented, what mechanisms of impact drove recruitment, what the role of context was, and how these components together influenced webRDS recruitment performance.
RESULTS
We included 18 studies from 8 countries, including both high and low-middle income countries, where 12 studies used webRDS for making population estimates, 3 for studying social network characteristics, and 3 for delivering health-related interventions. Studies used webRDS to recruit between 19 and 3448 participants from a variety of target populations. Studies differed greatly in the numbers of seeds recruited, the proportion of successfully recruiting participants, the numbers of recruitment waves, the types of incentives offered to participants, and the duration of data collection. Studies that recruited relatively more seeds, through online platforms, and with less rigorous selection procedures, reported relatively low percentages of successfully recruiting seeds. Studies that did not offer at least one guaranteed material incentive reported relatively fewer waves and lower percentages of successfully recruiting participants. The time of data collection was shortest in studies with university students.
CONCLUSIONS
WebRDS can be successfully applied to recruit individuals for making population estimates, studying social network characteristics, and delivering health interventions. In general, seed and peer-recruitment may be enhanced by rigorously selecting and motivating seeds, offering at least one guaranteed material incentive, and facilitating adequate recruitment options in regards to target populations’ online connectedness and communication behavior. Potential trade-offs should be taken into account when implementing webRDS. Examples are recruiting many seeds and less opportunities for rigorous seed selection procedures, as well as issues around online rather than physical participation, such as risks of system cheaters through repeat participation.
CLINICALTRIAL