title: Recruitment-adjusted estimates of HIV prevalence and risk among men who have sex with men: effects of weighting venue-based sampling data.
abstract: OBJECTIVE
  We investigated the impact of recruitment bias within the venue-based sampling (VBS) method, which is widely used to estimate disease prevalence and risk factors among groups, such as men who have sex with men (MSM), that congregate at social venues.
  
  
  METHODS
  In a 2008 VBS study of 479 MSM in New York City, we calculated venue-specific approach rates (MSM approached/MSM counted) and response rates (MSM interviewed/MSM approached), and then compared crude estimates of HIV risk factors and seroprevalence with estimates weighted to address the lower selection probabilities of MSM who attend social venues infrequently or were recruited at high-volume venues.
  
  
  RESULTS
  Our approach rates were lowest at dance clubs, gay pride events, and public sex strolls, where venue volumes were highest; response rates ranged from 39% at gay pride events to 95% at community-based organizations. Sixty-seven percent of respondents attended MSM-oriented social venues at least weekly, and 21% attended such events once a month or less often in the past year. In estimates adjusted for these variations, the prevalence of several past-year risk factors (e.g., unprotected anal intercourse with casual/exchange partners, ≥5 total partners, group sex encounters, at least weekly binge drinking, and hard-drug use) was significantly lower compared with crude estimates. Adjusted HIV prevalence was lower than unadjusted prevalence (15% vs. 18%), but not significantly.
  
  
  CONCLUSIONS
  Not adjusting VBS data for recruitment biases could overestimate HIV risk and prevalence when the selection probability is greater for higher-risk MSM. While further examination of recruitment-adjustment methods for VBS data is needed, presentation of both unadjusted and adjusted estimates is currently indicated.
authors: New York City Department of Health and Mental Hygiene, New York, NY, USA. sjenness@uw.edu
authors: Samuel M
authors: SM
authors: Jenness
authors: Alan
authors: A
authors: Neaigus
authors: Christopher S
authors: CS
authors: Murrill
authors: Camila
authors: C
authors: Gelpi-Acosta
authors: Travis
authors: T
authors: Wendel
authors: Holly
authors: H
authors: Hagan
mesh_terms: D000293:Adolescent; D000328:Adult; D040343:Behavioral Risk Factor Surveillance System; D015982:Bias; D001727:Bisexuality; D015658:HIV Infections / Q000453:epidemiology* / Q000635:transmission; D018451:Homosexuality, Male; D006801:Humans; D008297:Male; D009519:New York City / Q000453:epidemiology; D018579:Patient Selection; D011159:Population Surveillance / Q000379:methods*; D015995:Prevalence; D018570:Risk Assessment; D012309:Risk-Taking; D012494:Sampling Studies; D016036:Seroepidemiologic Studies; D014505:Urban Population / Q000706:statistics & numerical data