Community mapping and respondent-driven sampling of gay and bisexual men's communities in Vancouver, Canada.

Literature suggests formative research is vital for those using respondent-driven sampling (RDS) to study hidden populations of interest. However, few authors have described in detail how different qualitative methodologies can address the objectives of formative research for understanding the social network properties of the study population, selecting seeds and adapting survey logistics to best fit the population. In this paper we describe the use of community mapping exercises as a tool within focus groups to collect data on social and sexual network characteristics of gay and bisexual men in the metropolitan area of Vancouver, Canada. Three key themes emerged from analysing community maps along with other formative research data: (1) connections between physical spaces and social networks of gay and bisexual men, (2) diversity in communities and (3) substance use linked to formation of sub-communities. We discuss how these themes informed the planning and operations of a longitudinal epidemiological cohort study recruited by RDS. We argue that using community mapping within formative research is a valuable qualitative tool for characterising network structures of a diverse and differentiated population of gay and bisexual men in a highly developed urban setting.