title: Representativeness of injecting drug users who participate in HIV surveillance: results from Australia's Needle and Syringe Program Survey.
abstract: OBJECTIVE
  Australia's annual Needle and Syringe Program (NSP) Survey forms the basis of HIV surveillance among injecting drug users (IDUs) by providing serial point prevalence estimates of patterns of infection and risk behaviors. This study examined the representativeness of NSP Survey samples.
  
  
  METHODS
  National cross-sectional survey of 3920 NSP clients.
  
  
  METHODS
  Demographic and drug use characteristics of respondents and nonrespondents to the 2006 Survey were compared.
  
  
  RESULTS
  Relative to NSP clients who last injected heroin, methamphetamine injectors were significantly more likely to complete the Survey, as were people who had last injected an opioid maintenance pharmacotherapy or morphine. Other variables independently associated with Survey completion were female gender and being aged >or=35 years. Although the median age of NSP Survey samples has increased by 1 year per annum since 2002, the increase has occurred among both repeat and first-time respondents, allaying concerns that an ageing cohort of NSP clients repeatedly completes the Survey and unduly influences its results.
  
  
  CONCLUSIONS
  Inferences derived from the Survey results can reasonably be applied to the population of NSP clients, although because older female pharmaceutic injectors may be overrepresented among NSP Survey participants, recruitment strategies to target specific subpopulations (younger male participants) and stratification of main outcomes by age and gender in future analyses may usefully be considered. Although the extent to which Survey results can be generalized to Australia's broader IDU population cannot be ascertained, their consistency with other sources of surveillance data suggests that NSP Survey samples reflect the changing characteristics of Australia's illicit drug markets. Consequently, these are likely to be as representative samples of injectors as it is practical to obtain, and the Australian NSP Survey provides a useful model for blood-borne virus surveillance among IDUs.
authors.affiliation: Viral Hepatitis Epidemiology and Prevention Program, National Centre in HIV Epidemiology and Clinical Research, University of New South Wales, Darlinghurst, New South Wales, Australia. libby.topp@justicehealth.nsw.gov.au
authors.forename: Libby
authors.initials: L
authors.lastname: Topp
authors.forename: Jenny
authors.initials: J
authors.lastname: Iversen
authors.forename: Handan
authors.initials: H
authors.lastname: Wand
authors.forename: Carolyn
authors.initials: C
authors.lastname: Day
authors.forename: John
authors.initials: J
authors.lastname: Kaldor
authors.forename: Lisa
authors.initials: L
authors.lastname: Maher
mesh_terms: D000328:Adult; D001315:Australia / Q000453:epidemiology; D003430:Cross-Sectional Studies; D005260:Female; D015658:HIV Infections / Q000453:epidemiology*; D006306:Health Surveys; D006801:Humans; D008297:Male; D018671:Needle-Exchange Programs / Q000706:statistics & numerical data*; D012307:Risk Factors; D012309:Risk-Taking; D015819:Substance Abuse, Intravenous / Q000453:epidemiology*