title: Absence of association between delayed type hypersensitivity to tuberculin and atopy in children in The Gambia.
abstract: BACKGROUND
  An inverse association between delayed type hypersensitivity to tuberculin and atopy has been observed in children, suggesting that exposure to mycobacteria may influence the immune response to allergens.
  
  
  OBJECTIVE
  To investigate the relationship between tuberculin responses and atopy in children living in three different environments in The Gambia.
  
  
  METHODS
  In this cross-sectional study a total of 507 school-aged children were recruited from rural, urban poor or urban affluent communities. They were assessed for skin responses to five common allergens and tuberculin, presence of bacille Calmette-Guérin (BCG) scar, presence of intestinal parasites, and total serum IgE. Atopy was defined as the presence of a skin prick test response > or = 3 x 3 mm to at least one allergen.
  
  
  RESULTS
  The overall prevalence of atopy was 33% but there was a significant variation among the three study groups. The prevalence of atopy was 22% in urban poor, 36% in urban affluent, and 43% in rural children. Controlling for potential confounding factors, children in the rural community had a significantly higher odds ratio, 3.3 (95% confidence interval 1.8-6.0) of being atopic than children from the urban poor community. No association between atopy and tuberculin response or BCG scar was observed in any of the three groups. Serum IgE levels were higher among children of the urban poor group but were not associated with tuberculin response or BCG scar in any of the groups.
  
  
  CONCLUSIONS
  Environmental factors have an important influence on the development of atopy in children in The Gambia but delayed type hypersensitivity to tuberculin is not a protective factor.
authors.affiliation: Medical Research Council Laboratories, The Gambia. mota@jhsph.edu
authors.forename: M O C
authors.initials: MO
authors.lastname: Ota
authors.forename: M A B
authors.initials: MA
authors.lastname: van der Sande
authors.forename: G E L
authors.initials: GE
authors.lastname: Walraven
authors.forename: D
authors.initials: D
authors.lastname: Jeffries
authors.forename: O A
authors.initials: OA
authors.lastname: Nyan
authors.forename: A
authors.initials: A
authors.lastname: Marchant
authors.forename: K P W J
authors.initials: KP
authors.lastname: McAdam
mesh_terms: D001500:BCG Vaccine / Q000008:administration & dosage; D002648:Child; D003430:Cross-Sectional Studies; D005260:Female; D005714:Gambia; D006801:Humans; D006967:Hypersensitivity / Q000453:epidemiology* / Q000276:immunology; D006968:Hypersensitivity, Delayed / Q000276:immunology; D007073:Immunoglobulin E / Q000097:blood; D007411:Intestinal Diseases, Parasitic / Q000276:immunology; D016015:Logistic Models; D008297:Male; D011203:Poverty; D015995:Prevalence; D012307:Risk Factors; D012423:Rural Health; D012882:Skin Tests; D014374:Tuberculin Test; D014504:Urban Health
chemical_list: D001500:BCG Vaccine; D007073:Immunoglobulin E