title: Factors associated with HIV seroconversion in gay men in England at the start of the 21st century.
abstract: OBJECTIVE
  To detect and quantify current risk factors for HIV seroconversion among gay men seeking repeat tests at sexual health clinics.
  
  
  METHODS
  Unmatched case control study conducted in London, Brighton and Manchester, UK.
  
  
  METHODS
  75 cases (recent HIV positive test following a negative test within the past 2 years) and 157 controls (recent HIV negative test following a previous negative test within the past 2 years) completed a computer-assisted self interview focused on sexual behaviour and lifestyle between HIV tests.
  
  
  RESULTS
  Cases and controls were similar in socio-demographics, years since commencing sex with men, lifetime number of HIV tests, reasons for seeking their previous HIV tests and the interval between last HIV tests (mean = 10.5 months). Risk factors between tests included unprotected receptive anal intercourse (URAI) with partners not believed to be HIV negative (adjusted odds ratio (AOR) and 95% confidence interval 4.1, 1.8 to 9.3), where increased risk was associated with concomitant use of nitrite inhalants, receiving ejaculate and increasing numbers of partners. Independent risk was also detected for unprotected insertive anal intercourse (UIAI) with more than one man (AOR 2.7, 1.3 to 5.5) and use of nitrite inhalants (AOR 2.4, 1.1 to 5.2).
  
  
  CONCLUSIONS
  HIV serodiscordant unprotected anal intercourse remains the primary context for HIV transmission among gay men, with increased risk associated with being the receptive partner, receiving ejaculate and use of nitrite inhalants. Although the HIV transmission risk of URAI is widely acknowledged, this study highlights the risk of UIAI and that nitrite inhalants may be an important facilitator of transmission when HIV exposure occurs.
authors.affiliation: HIV and STI Department, Health Protection Agency Centre for Infections, UK. n.macdonald@imperial.ac.uk
authors.forename: N
authors.initials: N
authors.lastname: Macdonald
authors.forename: G
authors.initials: G
authors.lastname: Elam
authors.forename: F
authors.initials: F
authors.lastname: Hickson
authors.forename: J
authors.initials: J
authors.lastname: Imrie
authors.forename: C A
authors.initials: CA
authors.lastname: McGarrigle
authors.forename: K A
authors.initials: KA
authors.lastname: Fenton
authors.forename: K
authors.initials: K
authors.lastname: Baster
authors.forename: H
authors.initials: H
authors.lastname: Ward
authors.forename: V L
authors.initials: VL
authors.lastname: Gilbart
authors.forename: R M
authors.initials: RM
authors.lastname: Power
authors.forename: B G
authors.initials: BG
authors.lastname: Evans
mesh_terms: D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D004739:England / Q000453:epidemiology; D006679:HIV Seropositivity / Q000453:epidemiology*; D018451:Homosexuality, Male / Q000706:statistics & numerical data*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012044:Regression Analysis; D012307:Risk Factors; D047568:Unsafe Sex / Q000706:statistics & numerical data