title: A comparison of respondent-driven and venue-based sampling of female sex workers in Liuzhou, China.
abstract: OBJECTIVE
  To compare two methods for sampling female sex workers (FSWs) for bio-behavioural surveillance. We compared the populations of sex workers recruited by the venue-based Priorities for Local AIDS Control Efforts (PLACE) method and a concurrently implemented network-based sampling method, respondent-driven sampling (RDS), in Liuzhou, China.
  
  
  METHODS
  For the PLACE protocol, all female workers at a stratified random sample of venues identified as places where people meet new sexual partners were interviewed and tested for syphilis. Female workers who reported sex work in the past 4 weeks were categorised as FSWs. RDS used peer recruitment and chain referral to obtain a sample of FSWs. Data were collected between October 2009 and January 2010. We compared the socio-demographic characteristics and the percentage with a positive syphilis test of FSWs recruited by PLACE and RDS.
  
  
  RESULTS
  The prevalence of a positive syphilis test was 24% among FSWs recruited by PLACE and 8.5% among those recruited by RDS and tested (prevalence ratio 3.3; 95% CI 1.5 to 7.2). Socio-demographic characteristics (age, residence and monthly income) also varied by sampling method. PLACE recruited fewer FSWs than RDS (161 vs 583), was more labour-intensive and had difficulty gaining access to some venues. RDS was more likely to recruit from areas near the RDS office and from large low prevalence entertainment venues.
  
  
  CONCLUSIONS
  Surveillance protocols using different sampling methods can obtain different estimates of prevalence and population characteristics. Venue-based and network-based methods each have strengths and limitations reflecting differences in design and assumptions. We recommend that more research be conducted on measuring bias in bio-behavioural surveillance.
authors.affiliation: The Carolina Population Center and Department of Epidemiology, Gillings School of Global Public Health, Campus Box 8120, University of North Carolina at Chapel Hill, Chapel Hill, NC 27546, USA. sharon_weir@unc.edu
authors.forename: Sharon S
authors.initials: SS
authors.lastname: Weir
authors.forename: M Giovanna
authors.initials: MG
authors.lastname: Merli
authors.forename: Jing
authors.initials: J
authors.lastname: Li
authors.forename: Anisha D
authors.initials: AD
authors.lastname: Gandhi
authors.forename: William W
authors.initials: WW
authors.lastname: Neely
authors.forename: Jessie K
authors.initials: JK
authors.lastname: Edwards
authors.forename: Chirayath M
authors.initials: CM
authors.lastname: Suchindran
authors.forename: Gail E
authors.initials: GE
authors.lastname: Henderson
authors.forename: Xiang-Sheng
authors.initials: XS
authors.lastname: Chen
mesh_terms: D000293:Adolescent; D000328:Adult; D002681:China; D004812:Epidemiologic Methods; D005260:Female; D006801:Humans; D008875:Middle Aged; D015995:Prevalence; D012494:Sampling Studies; D060386:Sex Workers; D013048:Specimen Handling / Q000379:methods; D013587:Syphilis / Q000175:diagnosis*; D055815:Young Adult