Age-dependent distribution of the atopic phenotype and allergen sensitization among asthmatic children in southern Taiwan.

BACKGROUND Asthma is divided into atopic and non-atopic phenotypes. The percentages of atopic asthma and allergen sensitization in patients of different ages have not been well studied. OBJECTIVE To determine the percentage distribution of atopic and non-atopic phenotypes in different age groups of asthmatic children, and investigate the distribution of specific IgE to different allergens when stratified by age group in southern Taiwan. METHOD We conducted this hospital-based, retrospective, cross-sectional study in southern Taiwan between 2004 and 2006. Asthmatic children aged 3 to 18 years who were diagnosed according to the Global Initiative for Asthma guidelines were enrolled. The MAST-CLA system was used to detect 36 allergen-specific IgEs. RESULTS A total of 620 asthmatic children were divided into three groups: preschool (3-6 years old, n=360), school-aged (7-12 years old, n=213), and adolescent (13-18 years old, n=41) children. The atopic and non-atopic phenotypes were observed in 54.8% and 45.2% of the asthmatic children, respectively. The atopic phenotype was observed in 45.6%, 65.7%, and 80.5% of the preschool, school-aged and adolescent groups, respectively. The percentages of the atopic phenotype were significantly different when stratified by age group (p<0.001), and there was a positive trend of percentage distribution. The percentages of sensitization to aeroallergens were significantly different and observed in 44.0%, 65.7%, and 80.5% of the preschool, school-aged and adolescent groups, respectively (p<0.001). There were positive trends between age groups and prevalence rates of sensitization to the main aeroallergen and other aeroallergen groups, but not to each allergen of the seafood or other food allergen group. CONCLUSIONS A trend of an increasing percentage of the atopic phenotype when stratified by age group was found in asthmatic children in southern Taiwan. Aeroallergens contributed more to pediatric asthma than food allergens. The prevalence of sensitization to aeroallergens increased with increasing age when stratified by age group.