title: Using respondent-driven sampling (RDS) to recruit illegal poly-substance users in Cape Town, South Africa: implications and future directions.
abstract: South Africa continues to witness an increase in illicit poly-substance use, although a precise measurement continues to be compounded by difficulties in accessing users. In a pilot attempt to use respondent-driven sampling (RDS)-a chain referral sampling method used to access populations of individuals who are 'hard-to-reach'-this article documents the feasibility of the method as recorded in a simultaneously run, multisite, poly-substance study in Cape Town. Here we aim to a) document the piloting of RDS among poly-substance users in the three socio-economic disparate communities targeted; b) briefly document the results; and c) review the utility of RDS as a research tool.
  
  
  
  Three cross-sectional surveys using standard RDS procedures were used to recruit active poly-substance users and were concurrently deployed in three sites. Formative research was initially conducted to assess the feasibility of the survey. To determine whether RDS could be used to successfully recruit poly-substance users, social network characteristics, such as network size was determined.
  
  
  
  A 42.5 % coupon return rate was recorded in total from 12 initial seeds. There were vast differences in the recruitment chains of individual seeds-two generated more than 90 recruits, and 2 of the 10 recruitment chains showing a length of more than 10 waves. Findings include evidence of the use of 3 or more substances in all three sites, high levels of unemployment among users, with more than a third of participants in two sites reporting arrest for drug use in the past 12 months.
  
  
  
  Our results indicate that RDS was a feasible and acceptable sampling method for recruiting participants who may not otherwise be accessible. Future studies can use RDS to recruit such cohorts, and the method could form part of broader efforts to document vulnerable populations.
authors: Alcohol, Tobacco and Other Drug Research Unit, South African Medical Research Council, P.O. Box 19070, Tygerberg, 7505, Cape Town, South Africa. nadine.harker@mrc.ac.za.|School of Public Health and Family Medicine, Falmouth Building, Faculty of Health Sciences University of Cape Town, 7701, Cape Town, South Africa. nadine.harker@mrc.ac.za.
authors: Nadine
authors: N
authors: Harker Burnhams
authors: Biostatistics Unit, South African Medical Research Council, P.O. Box 19070, Tygerberg, Cape Town, 7505, South Africa.
authors: Ria
authors: R
authors: Laubscher
authors: Centre for Criminology, University of Cape Town Rondebosch, Private Bag x3, Cape Town, 7701, South Africa.|Centre of Criminology, Private Bag x3, Cape Town, 7701, South Africa.
authors: Simon
authors: S
authors: Howell
authors: Centre for Criminology, University of Cape Town Rondebosch, Private Bag x3, Cape Town, 7701, South Africa.|Centre of Criminology, Private Bag x3, Cape Town, 7701, South Africa.
authors: Mark
authors: M
authors: Shaw
authors: Alcohol, Tobacco and Other Drug Research Unit, South African Medical Research Council, P.O. Box 19070, Tygerberg, 7505, Cape Town, South Africa.
authors: Jodilee
authors: J
authors: Erasmus
authors: Health Systems Research Unit, South African Medical Research Council, P.O. Box 19070, Tygerberg, Cape Town, 7505, South Africa.
authors: Loraine
authors: L
authors: Townsend
mesh_terms: D000293:Adolescent; D000328:Adult; D003415:Crime; D003430:Cross-Sectional Studies; D055030:Drug Users / Q000706:statistics & numerical data*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008297:Male; D018579:Patient Selection; D010865:Pilot Projects; D012944:Social Support; D013019:South Africa; D011795:Surveys and Questionnaires; D014478:Unemployment; D055815:Young Adult
keywords: Illicit Drugs; Poly-substances; Respondent-driven sampling; South Africa