title: HIV incidence estimate combining HIV/AIDS surveillance, testing history information and HIV test to identify recent infections in Lazio, Italy.
abstract: BACKGROUND
  The application of serological methods in HIV/AIDS routine surveillance systems to identify persons with recently acquired HIV infection has been proposed as a tool which may provide an accurate description of the current transmission patterns of HIV. Using the information about recent infection it is possible to estimate HIV incidence, according to the model proposed by Karon et al. in 2008, that accounts for the effect of testing practices on the number of persons detected as recently infected.
  
  
  METHODS
  We used data from HIV/AIDS surveillance in the period 2004-2008 to identify newly diagnosed persons. These were classified with recent/non-recent infection on the basis of an avidity index result, or laboratory evidence of recently acquired infection (i.e., previous documented negative HIV test within 6 months; or presence of HIV RNA or p24 antigen with simultaneous negative/indeterminate HIV antibody test). Multiple imputation was used to impute missing information. The incidence estimate was obtained as the number of persons detected as recently infected divided by the estimated probability of detection. Estimates were stratified by calendar year, transmission category, gender and nationality.
  
  
  RESULTS
  During the period considered 3,633 new HIV diagnoses were reported to the regional surveillance system. Applying the model, we estimated that in 2004-2008 there were 5,465 new infections (95%CI: 4,538-6,461); stratifying by transmission category, the estimated number of infections was 2,599 among heterosexual contacts, 2,208 among men-who-have-sex-with-men, and 763 among injecting-drug-users. In 2008 there were 952 (625-1,229) new HIV infections (incidence of 19.9 per 100,000 person-years). In 2008, for men-who-have-sex-with-men (691 per 100,000 person-years) and injecting drug users (577 per 100,000 person-years) the incidence remained comparatively high with respect to the general population, although a decreasing pattern during 2004-2008 was observed for injecting-drug-users.
  
  
  CONCLUSIONS
  These estimates suggest that the transmission of HIV infection in Lazio remains frequent and men-who-have-sex-with men and injecting-drug-users are still greatly affected although the majority of new infections occurs among heterosexual individuals.
authors.affiliation: Istituto Nazionale per le Malattie Infettive Lazzaro Spallanzani, Rome, Italy. alessia.mammone@inmi.it
authors.forename: Alessia
authors.initials: A
authors.lastname: Mammone
authors.forename: Patrizio
authors.initials: P
authors.lastname: Pezzotti
authors.forename: Claudio
authors.initials: C
authors.lastname: Angeletti
authors.forename: Nicoletta
authors.initials: N
authors.lastname: Orchi
authors.forename: Angela
authors.initials: A
authors.lastname: Carboni
authors.forename: Assunta
authors.initials: A
authors.lastname: Navarra
authors.forename: Maria R
authors.initials: MR
authors.lastname: Sciarrone
authors.forename: Catia
authors.initials: C
authors.lastname: Sias
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Puro
authors.forename: Gabriella
authors.initials: G
authors.lastname: Guasticchi
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Ippolito
authors.forename: Piero
authors.initials: P
authors.lastname: Borgia
authors.forename: Enrico
authors.initials: E
authors.lastname: Girardi
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D019411:Clinical Laboratory Techniques / Q000379:methods; D004812:Epidemiologic Methods; D005260:Female; D015658:HIV Infections / Q000175:diagnosis / Q000453:epidemiology* / Q000635:transmission; D018451:Homosexuality, Male; D006801:Humans; D015994:Incidence; D007558:Italy / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D015819:Substance Abuse, Intravenous / Q000150:complications; D055815:Young Adult