The utility of non-proportional quota sampling for recruiting at-risk women for microbicide research

In the context of a measurement development study designed to contextualize microbicide acceptability, a sample that represented a range of at-risk women and maintained the statistical power needed for validity analyses was required. A non-proportional quota sampling strategy focused on race/ethnicity and number of sexual partners was utilized. This strategy resulted in enrollment of approximately equal proportions of Latina (31%), Black (36%), and White (32%) women, and an approximately 1:2 ratio of single-partnered (29%) and multi-partnered (71%) women. About 17% of women screened were ineligible based on eligibility criteria; an additional 16% were ineligible based on quota closures. Most participants were recruited through word of mouth (39%), community-based organizations (19%), or media sources (19%). Women recruited through word of mouth had the highest screen-to-interview completion percentage (67%). Non-proportional quota sampling is a feasible option for ensuring adequate representation of sample characteristics in microbicide research, but this goal should be weighed against cost and staff burden.