Sex workers (methods)

toolkit material

As indicated in the mapping report, very few countries in Europe report behavioural surveillance among sex workers.

Two main methodological options have been used:

  • surveys among convenience samples of sex workers (mainly female); these will be presented below 
  • insertion of a batch of questions related to the occurrence of sexual intercourse with sex workers, directed at men (mainly) in representative surveys in the general population (see general population methods)

Table 1 describes selected features of available methods for collecting behavioural data among sex workers.

Table 2 presents the best three methods proposed by the experts according to two different contexts

Table 1. Selected features of available methods for collecting behavioural data among among sex workers

Design Advantages Disadvantages Comments
Service-based (a)  
  • Inclusive of sex workers from different sectors (e.g. indoor and outdoor)
  • Can be linked to (and lever for) preventive interventions
  • Possible second generation surveillance with data on STI/HIV
  • Sustainable (as long as services provided)
  • Bias towards those with better motivation and access to care
  • May exclude migrants/ illegal
  • Possible bias towards those with infections
  • Hard to relate to denominator and may be difficult to use for comparisons and trends if there are changes in health service organisation/access
  • Is dependent on disclosure and recording of sex work status
  • Dependent on existence of acceptable and accessible services for sex workers
  • Need assurances about confidentiality of patient data
Sex work venue-based (b)   
  • Can be inclusive of sex workers from different sectors (e.g. indoor and outdoor)
  • Can be related to a denominator
  • Can be linked to preventive interventions
  • Often limited to the most visible sex workers (e.g. street) and therefore produces a biased sample
  • Will exclude more isolated workers
  • Some sex workers may be reluctant to participate
  • Dependent on cooperation with sex work managers who may be reluctant to cooperate
  • Should be done following mapping of sex work to ensure appropriate sampling, for example time location sampling (TLS)
  • Need assurance about confidentiality
Respondent driven sampling (RDS) (c)   
  • A way of including “hidden” populations
  • Is a systematic way of sampling
  • May provide estimates of population size
  • Recruitment often slow and unpredictable
  • Analysis statistically difficult due to weighting issues

Largely used for research rather than surveillance

Internet (d)
  • Should be a way of accessing a wide population, including the large numbers who advertise on the internet
  • Once established is relatively cheap
  • Confidential 
  • Unlinked to interventions
  • Depends on internet access/ coverage of the population
  • Not linked to testing therefore not suitable for SGS

Not yet piloted in sex workers but proved effective in MSM

 

Examples
(a) Service-based
Ward H, Day S, Green A, Cooper K, Weber J. Declining prevalence of STI in the London sex industry, 1985 to 2002. Sex Transm Infect 2004;80(5):374-6.

Sethi G, Holden BM, Gaffney J, Greene L, Ghani AC, Ward H. HIV, sexually transmitted infections and risk behaviours in male sex workers in London over a 10 year period. Sex Transm Infect 2006;82(5):359-63.

(b) Sex work venue-based
Folch C, Esteve A, Sanclemente C, Martró E, Lugo R, Molinos S, Gonzalez V, Ausina V, Casabona J. Prevalence of human immunodeficiency virus, Chlamydia trachomatis, and Neisseria gonorrhoeae and risk factors for sexually transmitted infections among immigrant female sex workers in Catalonia, Spain. Sex Transm Dis 2008;35(2):178-83. 

Mills S, Saidel T, Magnani R, et al.. Surveillance and modelling of HIV, STI, and risk behaviours in concentrated HIV epidemics. Sex Transm Infect 2004;80(Suppl 2):ii 57–62

(c) Respondent driven sampling (RDS)
Uuskula A, Fischer K, Raudne R, Kilgi H, Krylov R, Salminen M, et al. A study on HIV and hepatitis C virus among commercial sex workers in Tallinn. Sex Transm Infect 2008;84(3):189-91. 

Johnston LG, Sabin K, Hien MT, Huong PT. Assessment of Respondent Driven Sampling for Recruiting Female Sex Workers in Two Vietnamese Cities: Reaching the Unseen Sex Worker. Journal of Urban Health 2006;83(7): i16-i28.

Internet
No studies published yet

The table below presents the best three methods proposed by the experts according to two different contexts:

  • the population is reachable in known settings and is not severely stigmatised
  • the population is not very well known, not easy to reach, and/or stigmatised.

Table 2. Best three methods to access sex workers according to context
(NB does not include clients, as these will be included in general population surveys)

   Best methods  Main indication for preference
  A. The population is reachable in known settings and is not severely stigmatised  
 1 Sex work venue-based Sex work venues can be mapped and a systematic sampling method applied
 2 Service-based Can reach sex workers from many different sectors including dispersed venues
 3 Internet Access to wide range of sex workers, and many sex workers and client meet via the internet (but methods not yet tested) 
  B. The population is not very well known, not easy to reach, and/or stigmatised  
 1 Service-based Health services often have contact with groups that are otherwise hidden, and can reach sex workers from a range of sectors
 2 Sex work venue-based Can be a rolling programme that combines mapping of sex work venues with survey
 3  RDS Could reach previously hidden sex workers by exploiting peer networks