title: A multilevel approach for assessing the variability of hepatitis C prevalence in injection drug users by their gathering places.
abstract: OBJECTIVE
  The aim of this study was to investigate the variation in hepatitis C virus (HCV) prevalence in injection drug users (IDUs) by their gathering places, using a multilevel approach.
  
  
  METHODS
  IDUs recruited from their gathering places were invited to respond to a questionnaire on demographics, drug use history, injection behaviors, and methadone treatment. Dried blood spots were collected for HCV antibody testing by ELISA. Factors associated with the anti-HCV test result were explored by linear logistic regression, followed by the evaluation of heterogeneity between gathering places by multilevel analysis.
  
  
  RESULTS
  A total of 622 respondents from 19 gathering places in Hong Kong, recruited between August and September 2011, were evaluated. Anti-HCV seroprevalence was 81.7% (95% confidence interval 78.6-84.7%), ranging from 67% to 100% by gathering place. HCV infection was associated with current practice of injection, needle-sharing, and midazolam injection. On multilevel analysis, there was a modest but significant variation in HCV antibody prevalence by gathering place, adjusted by midazolam injection (adjusted odds ratio (AOR) 3.91) and current injection (AOR 2.88) or injection over a long duration (AOR 3.17).
  
  
  CONCLUSIONS
  There was heterogeneity in HCV antibody prevalence in IDUs by gathering place, while the influence of injection behaviors varied, suggesting interactivity between factors at the individual and group levels.
authors.affiliation: Stanley Ho Centre for Emerging Infectious Diseases, Prince of Wales Hospital, The Chinese University of Hong Kong, 30-32 Ngan Shing Street, Shatin, Hong Kong.
authors.forename: Ngai Sze
authors.initials: NS
authors.lastname: Wong
authors.forename: Pui Chung
authors.initials: PC
authors.lastname: Chan
authors.forename: Shui Shan
authors.initials: SS
authors.lastname: Lee
authors.forename: See Long
authors.initials: SL
authors.lastname: Lee
authors.forename: Chi Kei
authors.initials: CK
authors.lastname: Lee
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D016174:Hepacivirus; D006526:Hepatitis C / Q000150:complications / Q000453:epidemiology*; D018937:Hepatitis C Antibodies / Q000097:blood; D006723:Hong Kong / Q000453:epidemiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D016485:Needle Sharing; D015995:Prevalence; D016036:Seroepidemiologic Studies; D015819:Substance Abuse, Intravenous / Q000150:complications* / Q000453:epidemiology*; D011795:Surveys and Questionnaires
chemical_list: D018937:Hepatitis C Antibodies