title: Examination of the risk of reinfection with hepatitis C among injecting drug users who have been tested in Glasgow.
abstract: BACKGROUND
  Unsafe injecting practices put injecting drug users (IDUs) at repeat exposure to infection with the hepatitis C virus (HCV). It has not yet been determined if spontaneously clearing one's primary infection influences the risk of reinfection; our aim was to estimate the relative risk of reinfection in IDUs who have cleared the virus.
  
  
  METHODS
  We conducted a retrospective study using a large database of HCV test results covering Greater Glasgow Health Board during 1993-2007 to calculate rates of infection and reinfection in current/former IDUs. The relative risk of (re)infection in previously infected compared with never-infected IDUs was estimated using Poisson regression, adjusting for age at study entry, sex, and calendar period of test.
  
  
  RESULTS
  Although the rate of reinfection in IDUs who were HCV antibody-positive, RNA-negative at baseline was lower (7/100 person-years, 95% CI: 5-9) than the rate of acute infection in IDUs who were HCV antibody-negative at baseline (10/100 person-years, 95% CI: 9-12), the risk of reinfection was not significantly different than the risk of initial infection (adjusted rate ratio=0.78, 95% CI: 0.57-1.08).
  
  
  CONCLUSIONS
  We found only weak evidence for a reduced risk of HCV reinfection in IDUs who had cleared their previous infection. Further research among those who have cleared infection through antiviral therapy is needed to help inform decisions regarding treatment of IDUs.
authors.affiliation: Health Protection Scotland, Meridian Court, 5 Cadogan Street, Glasgow G26QE, Scotland, UK. smcdonald4@nhs.net
authors.forename: Scott A
authors.initials: SA
authors.lastname: McDonald
authors.forename: Sharon J
authors.initials: SJ
authors.lastname: Hutchinson
authors.forename: Sheila O
authors.initials: SO
authors.lastname: Cameron
authors.forename: Hamish A
authors.initials: HA
authors.lastname: Innes
authors.forename: Allan
authors.initials: A
authors.lastname: McLeod
authors.forename: David J
authors.initials: DJ
authors.lastname: Goldberg
mesh_terms: D000328:Adult; D000998:Antiviral Agents / Q000627:therapeutic use*; D016208:Databases, Factual; D005260:Female; D016174:Hepacivirus / Q000276:immunology; D006526:Hepatitis C / Q000188:drug therapy / Q000453:epidemiology*; D006801:Humans; D015994:Incidence; D008297:Male; D016012:Poisson Distribution; D012367:RNA, Viral / Q000097:blood; D012008:Recurrence; D012044:Regression Analysis; D012189:Retrospective Studies; D012306:Risk; D012606:Scotland / Q000453:epidemiology; D015819:Substance Abuse, Intravenous / Q000150:complications*; D055815:Young Adult
chemical_list: D000998:Antiviral Agents; D012367:RNA, Viral