title: Sensitivity is not an intrinsic property of a diagnostic test: empirical evidence from histological diagnosis of Helicobacter pylori infection.
abstract: BACKGROUND
  We aimed to provide empirical evidence of how spectrum effects can affect the sensitivity of histological assessment of Helicobacter pylori infection, which may contribute to explain the heterogeneity in prevalence estimates across populations with expectedly similar prevalence.
  
  
  METHODS
  Cross-sectional evaluation of dyspeptic subjects undergoing upper digestive endoscopy, including collection of biopsy specimens from the greater curvature of the antrum for assessment of H. pylori infection by histopathological study and polymerase chain reaction (PCR), from Portugal (n = 106) and Mozambique (n = 102) following the same standardized protocol.
  
  
  RESULTS
  In the Portuguese sample the prevalence of infection was 95.3% by histological assessment and 98.1% by PCR. In the Mozambican sample the prevalence was 63.7% and 93.1%, respectively. Among those classified as infected by PCR, the sensitivity of histological assessment was 96.2% among the Portuguese and 66.3% among the Mozambican. Among those testing positive by both methods, 5.0% of the Portuguese and 20.6% of the Mozambican had mild density of colonization.
  
  
  CONCLUSIONS
  This study shows a lower sensitivity of histological assessment of H. pylori infection in Mozambican dyspeptic patients compared to the Portuguese, which may be explained by differences in the density of colonization, and may contribute to explain the heterogeneity in prevalence estimates across African settings.
authors.affiliation: Department of Hygiene and Epidemiology, University of Porto Medical School, Porto, Portugal. nlunet@med.up.pt
authors.forename: Nuno
authors.initials: N
authors.lastname: Lunet
authors.forename: Bárbara
authors.initials: B
authors.lastname: Peleteiro
authors.forename: Carla
authors.initials: C
authors.lastname: Carrilho
authors.forename: Céu
authors.initials: C
authors.lastname: Figueiredo
authors.forename: Ana
authors.initials: A
authors.lastname: Azevedo
mesh_terms: D000328:Adult; D001706:Biopsy; D003430:Cross-Sectional Studies; D003955:Diagnostic Tests, Routine; D004415:Dyspepsia / Q000382:microbiology; D005260:Female; D016481:Helicobacter Infections / Q000453:epidemiology* / Q000473:pathology*; D016480:Helicobacter pylori; D006801:Humans; D008297:Male; D008875:Middle Aged; D009073:Mozambique / Q000453:epidemiology; D011174:Portugal / Q000453:epidemiology; D015995:Prevalence; D011706:Pyloric Antrum / Q000473:pathology; D012680:Sensitivity and Specificity