To achieve the UNAIDS 90-90-90 target, key populations, such as men who have sex with men (MSM) and people who inject drugs (PWID) in low- and middle-income countries, must be reached. Respondent-driven sampling (RDS), a chain-referral strategy, is an established epidemiologic tool to characterize epidemics in hidden populations. We explore the ability of RDS to identify unaware HIV-positive persons over successive recruitment waves and its ability to reach people in all regions of medium to large cities in India.
We conducted RDS surveys in 27 Indian cities (12 MSM, 15 PWID). Individuals were eligible if they were age ≥ 18 years and reported recent MSM behavior (MSM sites) or drug injection (PWID sites). We initiated each RDS with 2-3 “seeds” per site, gave participants two coupons to recruit network members, and continued recruitment until 1000 subjects were enrolled. Participants completed a survey and were tested for HIV. We assessed the ability of RDS to identify HIV-positive persons unaware of their status across recruitment waves and created zip code maps of recruitment using ArcGIS.
We recruited 26,503 participants (12,022 MSM and 14,481 PWID) from 27 cities, over a median (range) of 112 days (52–200) and 21 recruitment waves (11–50). Of 4,065 HIV-positive persons identified, 2,325 (57%) were unaware of their status. While HIV prevalence was relatively stable across recruitment waves (~15%), the percentage of HIV-positive persons unaware of their status increased from 47% in waves 1-5 to 78% in waves >25 (p<0.001), suggesting identification of persons with poor service access as recruitment progressed deeper within networks. Further, despite recruiting from a single venue in each city, RDS reached individuals across all zip codes, with most zones reached within 5 recruitment waves (Figure). For example, in Chennai, participants were recruited from a median of 4.2 km from the study site, with 50 participants recruited from >20 km away.
Beginning with 2 or 3 “seeds” and recruiting from a single venue, RDS demonstrated the ability 1) to efficiently identify HIV-positive persons who were unaware of their status (with an increasing likelihood of identifying such persons in later recruitment waves), and 2) to reach MSM and PWID throughout all geographical regions in medium to large cities. Combined with evidence-based linkage strategies, RDS has the potential to improve the care continuum in key populations in low- and middle-income countries.