title: High prevalence of self-reported undiagnosed HIV despite high coverage of HIV testing: a cross-sectional population based sero-survey in South Africa.
abstract: OBJECTIVE
  To measure HIV prevalence and uptake of HIV counseling and testing (HCT) in a peri-urban South African community. To assess predictors for previous HIV testing and the association between the yield of previously undiagnosed HIV and time of last negative HIV test
  
  
  METHODS
  A random sample of 10% of the adult population (≥15 years) were invited to attend a mobile HCT service. Study procedures included a questionnaire, HIV testing and CD4 counts. Predictors for previous testing were determined using a binominal model.
  
  
  RESULTS
  1,144 (88.0%) of 1,300 randomly selected individuals participated in the study. 71.0% (68.3-73.6) had previously had an HIV test and 37.5% (34.6-40.5) had tested in the past 12 months. Men, migrants and older (>35 years) and younger (<20 years) individuals were less likely to have had a previous HIV test. Overall HIV prevalence was 22.7 (20.3-25.3) with peak prevalence of 41.8% (35.8-47.8) in women aged 25.1-35 years and 37.5% (26.7-48.3) in men aged 25.1-45 years. Prevalence of previously undiagnosed HIV was 10.3% (8.5-12.1) overall and 4.5% (2.3-6.6), 8.0% (CI 3.9-12.0) and 20.0% (13.2-26.8) in individuals who had their most recent HIV test within 1, 1-2 and more than 2 years prior to the survey.
  
  
  CONCLUSIONS
  The high burden of undiagnosed HIV in individuals who had recently tested underscores the importance of frequent repeat testing at least annually. The high prevalence of previously undiagnosed HIV in individuals reporting a negative test in the 12 months preceding the survey indicates a very high incidence. Innovative prevention strategies are needed.
authors.affiliation: Department of Clinical Research Unit, London School of Hygiene and Tropical Medicine, London, United Kingdom. katharina.kranzer@lshtm.ac.uk
authors.forename: Katharina
authors.initials: K
authors.lastname: Kranzer
authors.forename: Nienke
authors.initials: N
authors.lastname: van Schaik
authors.forename: Unice
authors.initials: U
authors.lastname: Karmue
authors.forename: Keren
authors.initials: K
authors.lastname: Middelkoop
authors.forename: Elaine
authors.initials: E
authors.lastname: Sebastian
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Lawn
authors.forename: Robin
authors.initials: R
authors.lastname: Wood
authors.forename: Linda-Gail
authors.initials: LG
authors.lastname: Bekker
mesh_terms: D015492:AIDS Serodiagnosis / Q000379:methods*; D000328:Adult; D003140:Communicable Disease Control; D003153:Community Health Services; D003430:Cross-Sectional Studies; D005260:Female; D015658:HIV Infections / Q000097:blood* / Q000175:diagnosis* / Q000453:epidemiology*; D006801:Humans; D015994:Incidence; D008297:Male; D008403:Mass Screening / Q000379:methods; D008875:Middle Aged; D015995:Prevalence; D015203:Reproducibility of Results; D013019:South Africa