title: HIV/AIDS knowledge among men who have sex with men: applying the item response theory.
abstract: OBJECTIVE
  To evaluate the level of HIV/AIDS knowledge among men who have sex with men in Brazil using the latent trait model estimated by Item Response Theory.
  
  
  METHODS
  Multicenter, cross-sectional study, carried out in ten Brazilian cities between 2008 and 2009. Adult men who have sex with men were recruited (n = 3,746) through Respondent Driven Sampling. HIV/AIDS knowledge was ascertained through ten statements by face-to-face interview and latent scores were obtained through two-parameter logistic modeling (difficulty and discrimination) using Item Response Theory. Differential item functioning was used to examine each item characteristic curve by age and schooling.
  
  
  RESULTS
  Overall, the HIV/AIDS knowledge scores using Item Response Theory did not exceed 6.0 (scale 0-10), with mean and median values of 5.0 (SD = 0.9) and 5.3, respectively, with 40.7% of the sample with knowledge levels below the average. Some beliefs still exist in this population regarding the transmission of the virus by insect bites, by using public restrooms, and by sharing utensils during meals. With regard to the difficulty and discrimination parameters, eight items were located below the mean of the scale and were considered very easy, and four items presented very low discrimination parameter (< 0.34). The absence of difficult items contributed to the inaccuracy of the measurement of knowledge among those with median level and above.
  
  
  CONCLUSIONS
  Item Response Theory analysis, which focuses on the individual properties of each item, allows measures to be obtained that do not vary or depend on the questionnaire, which provides better ascertainment and accuracy of knowledge scores. Valid and reliable scales are essential for monitoring HIV/AIDS knowledge among the men who have sex with men population over time and in different geographic regions, and this psychometric model brings this advantage.
authors.affiliation: Secretaria Municipal de Saúde de Belo Horizonte, Belo Horizonte, MG, Brasil.
authors.forename: Raquel Regina de Freitas Magalhães
authors.initials: RR
authors.lastname: Gomes
authors.affiliation: Faculdade de Educação, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brasil.
authors.forename: José Rodrigues
authors.initials: JR
authors.lastname: Batista
authors.affiliation: Faculdade de Medicina, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brasil.
authors.forename: Maria das Graças Braga
authors.initials: Md
authors.lastname: Ceccato
authors.affiliation: Departamento de Saúde Comunitária, Faculdade de Medicina, Universidade Federal do Ceará, Fortaleza, CE, Brasil.
authors.forename: Lígia Regina Franco Sansigolo
authors.initials: LR
authors.lastname: Kerr
authors.affiliation: Faculdade de Medicina, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brasil.
authors.forename: Mark Drew Crosland
authors.initials: MD
authors.lastname: Guimarães
mesh_terms: D000163:Acquired Immunodeficiency Syndrome / Q000517:prevention & control* / Q000635:transmission; D000328:Adult; D001938:Brazil; D003430:Cross-Sectional Studies; D015658:HIV Infections / Q000517:prevention & control* / Q000635:transmission; D007722:Health Knowledge, Attitudes, Practice; D018451:Homosexuality, Male; D006801:Humans; D008297:Male; D012959:Socioeconomic Factors; D011795:Surveys and Questionnaires