Sensitization to aeroallergens and asthma severity in the tropics

Background. The allergic asthma phenotype is the most extensively investigated. However, few studies have explored the association between sensitization to different aeroallergens, asthma severity and blood eosinophil counts, an important biomarker of Type 2 inflammation. This study aims to evaluate associations between sensitization to aeroallergens, severity of asthma, eosinophilic phenotypes and age of onset of symptoms. Methods. This was a cross-sectional study involving a tropical urban population sample. We included 450 individuals with mild asthma (MA) and 441 with moderate to severe asthma (MSA). Serum-specific IgE to nine aeroallergens was measured by the ImmunoCap™. We considered a cut-off point of 0.70 KU/L for mites and 0.35 KU/L for all other allergens. Blood eosinophilia was considered if the count was > 260 cells/mm³, and the age of onset was defined as early (EO < 12 years) and late (LO greater/equal 12 years). Results. Patients with asthma sensitive to dust mites, B. germanica and those with polysensitization are 1.6 to 1.8-fold more likely to have MSA, while in cases of sensitization to A. fumigatus this probability increases to 3-fold. Regarding the eosinophilic phenotype, individuals with MA sensitized to dust mites, B. germanica, dog epithelium and polysensitized individuals are more likely to present the eosinophilic phenotype (p < 0.05). However, we did not observe any association between sensitization to different aeroallergens and age of symptom onset (p > 0.05). Conclusions. We conclude that polysensitization or sensitization to mites, B. germanica, and mainly to A. fumigatus, are associated with the severity of asthma. Only in individuals with mild asthma, sensitization to dust mites, B. germanica, dog epithelium and polysensitization is associated with eosinophilic asthma. No sensitization profile was associated with the age of onset of asthma symptoms.