title: Evidence of an association between the O blood group and allergic rhinitis.
abstract: OBJECTIVE
  The aim of this study was to verify if ABO phenotypes are associated with allergic rhinitis.
  
  
  METHODS
  168 patients with allergic rhinitis and 168 control individuals from the same geographical region and paired by gender and age were enrolled in the study. ABO phenotypes were identified in red blood cells using the hemagglutination technique. The Fisher exact and chi-squared tests were employed to compare proportions. Statistical significance was set for an alpha error of 5% (p-value < 0.05).
  
  
  RESULTS
  The overall differences in the frequencies of the ABO phenotypes of patients and controls were marginal (χ(2): 7.569; degrees of freedom (DF): 3; p-value = 0.055) however the O blood group was associated with allergic rhinitis (χ(2): 5.764; DF: 1; p-value = 0.016; OR: 1.735; CI 95%: 1.127-2.673). The differences in the frequencies of the O phenotype in patients and controls were statistically different for men (χ(2): 8.520; DF: 1; p-value = 0.003) but not for women (χ(2): 0.6375; DF: 1; p-value = 0.4246). The A phenotype was associated with protection (OR: 0.4385; CI 95%: 0.2043-0.9415; p-value = 0.049) and the O phenotype was associated with susceptibility (OR = 2.789; CI 95%: 1.385-5.616; p-value = 0.005) to allergic rhinitis only for men.
  
  
  CONCLUSIONS
  The O blood group phenotype is associated with allergic rhinitis in male but not in female patients.
authors.affiliation: Immunogenetics Laboratory, Molecular Biology Department, Faculdade de Medicina de São José do Rio Preto - FAMERP, São José do Rio Preto, SP, Brazil.
authors.forename: Nelson
authors.initials: N
authors.lastname: Falsarella
authors.forename: Ana Iara da Costa
authors.initials: AI
authors.lastname: Ferreira
authors.forename: Fabiana
authors.initials: F
authors.lastname: Nakashima
authors.forename: Cinara de Cássia Brandão
authors.initials: Cde C
authors.lastname: de Mattos
authors.forename: Luiz Carlos
authors.initials: LC
authors.lastname: de Mattos