title: How atopic is atopic dermatitis?
abstract: BACKGROUND
  The extent to which the phenotype of atopic dermatitis (AD) is truly atopic has been the subject of much debate.
  
  
  OBJECTIVE
  We sought to systematically evaluate the evidence for the value of measurement of IgE antibodies in diagnosing AD and whether knowledge of IgE sensitization increases clinical diagnostic and predictive ability.
  
  
  METHODS
  We searched Medline from its inception until September 2003. Only studies that measured atopy as either skin prick test positivity or IgE-antibody sensitization to environmental allergens were included within a descriptive analysis. Because the small number of studies of adequate quality did not allow a formal meta-analysis, we assigned strength of evidence according to predefined quality criteria and ranked studies accordingly.
  
  
  RESULTS
  Inclusion of atopy as part of the diagnostic criteria for AD did not enhance the criteria's sensitivity and specificity in relation to the clinical phenotype of AD. The strength of association between atopy and AD varied significantly between hospital studies (47% to 75%; n=14 studies) and was stronger in hospital than in community populations (7.4% to 78%; n=13 studies). Whereas study quality did not have an effect on atopy prevalence in hospital populations, low atopy prevalences in community surveys were seen in less rigidly conducted studies. AD severity was positively associated with the number of positive skin prick test responses or IgE-antibody levels in 7 of 8 studies that measured both. Only one study suggested that IgE-specific sensitization to hen's egg is associated with subsequent development of AD, and 2 studies found that allergen-specific IgE sensitization in patients with AD is a prognostic marker for allergic airway disease in later life. Atopy-associated AD might also have a worse long-term prognosis than AD that is not associated with atopy.
  
  
  CONCLUSIONS
  Although atopy is clearly associated with AD, the role of IgE sensitization in AD needs further study. Current evidence suggests that up to two thirds of persons with AD are not atopic, which implies that continued use of the term atopic dermatitis is problematic. Longitudinal studies are needed to compare the treatment response and prognosis of IgE-associated and non-IgE-associated AD.
authors.affiliation: Centre of Evidence Based Dermatology, University of Nottingham, United Kingdom. carsten.flohr@nottingham.ac.uk
authors.forename: Carsten
authors.initials: C
authors.lastname: Flohr
authors.forename: S G O
authors.initials: SG
authors.lastname: Johansson
authors.forename: Carl-Fredrik
authors.initials: CF
authors.lastname: Wahlgren
authors.forename: Hywel
authors.initials: H
authors.lastname: Williams
mesh_terms: D003876:Dermatitis, Atopic / Q000175:diagnosis* / Q000276:immunology*; D006801:Humans; D007073:Immunoglobulin E / Q000097:blood / Q000276:immunology; D011237:Predictive Value of Tests
chemical_list: D007073:Immunoglobulin E