title: Risk factor analysis and serological diagnosis of HIV-1/HIV-2 infection in a Brazilian blood donor population: validation of the World Health Organization strategy for HIV testing.
abstract: OBJECTIVE
  To determine the relative prevalence of HIV-1 and HIV-2 and to evaluate the World Health Organization testing strategy for HIV diagnosis in a low-risk population in Brazil. In addition, to assess risk factors for HIV infection.
  
  
  METHODS
  Sera obtained from 9885 consecutive blood donors were screened in parallel by two HIV enzyme-linked immunosorbent assays (ELISA) with different antigen composition and test principles (Ortho HIV-1 and Wellcozyme HIV-1/2). Samples reactive to either ELISA were submitted to a Western blot assay and to a rapid HIV-1/2 ELISA (Sero-Immuno Diagnostics). An ELISA test with specific HIV-1/HIV-2-derived synthetic peptide was used to discriminate between samples reactive on the Wellcozyme HIV-1/2 assay. Demographic and serological data were used to address risk factors for HIV infection.
  
  
  RESULTS
  All the 28 Western blot-confirmed positive samples were reactive in both Ortho HIV-1 and Wellcozyme HIV-1/2 assays (sensitivity, 100%). The Wellcozyme HIV-1/2 specificity (99.9%) was higher than Ortho HIV-1 (99.5%). If sample reactivity to both tests was considered positive, the sensitivity and specificity of the screening would be 100%. However, further analysis with a third rapid HIV-1/2 ELISA reduced both the sensitivity and the specificity of the sequential testing strategy. Discrimination between HIV-1 and HIV-2 showed evidence for the presence of HIV-1 only. Finally, in the group aged 18-35 years, the presence of serological markers of hepatitis C virus and hepatitis B virus infections and the elevated levels of beta 2-microglobulin were variables associated with the identification of HIV-1-seropositive blood donors.
  
  
  CONCLUSIONS
  In a low-risk population, application of two high quality ELISA tests with different antigens and test principles can replace the use of the Western blot. In addition to the cost being reduced by 10-16%, a rapid diagnosis and the absence of indeterminate Western blot results confer an advantage to this strategy.
authors.affiliation: Hemotherapy Service, Hospital Israelita Albert Einstein, Sao Paulo, Brazil.
authors.forename: M B
authors.initials: MB
authors.lastname: Carvalho
authors.forename: N
authors.initials: N
authors.lastname: Hamerschlak
authors.forename: R S
authors.initials: RS
authors.lastname: Vaz
authors.forename: O C
authors.initials: OC
authors.lastname: Ferreira
mesh_terms: D000328:Adult; D000465:Algorithms; D001782:Blood Donors; D015153:Blotting, Western; D001938:Brazil / Q000453:epidemiology; D004797:Enzyme-Linked Immunosorbent Assay; D005069:Evaluation Studies as Topic; D017408:Guidelines as Topic; D015658:HIV Infections / Q000175:diagnosis / Q000453:epidemiology / Q000517:prevention & control*; D015497:HIV-1; D015498:HIV-2; D006801:Humans; D008403:Mass Screening / Q000379:methods*; D015995:Prevalence; D012307:Risk Factors; D012680:Sensitivity and Specificity; D014944:World Health Organization