Background: Early onset of asthma has been associated with an allergic phenotype whereas late onset with the eosinophilic phenotype. Our aim was to describe the distribution of phenotypes according to the onset of asthma symptoms in adult patients evaluated at the interdisciplinary Severe Asthma Board of the Fundación Neumológica Colombiana in Bogota.

Methods: Cross-sectional study that included all patients evaluated in the severe asthma board since 2019. Early-onset was an initiation of asthmatic symptoms at 12 years of age or younger and late-onset after that age. Phenotypes were defined as follows: Eosinophilic, blood eosinophils ?300 cells/µL; Allergic, total IgE?100IU/mL and positive allergy tests and Overlap criteria met for both previous definitions.

Results: 163 patients were included, 66.8% were female, 74.8% had late onset, 60.1% were allergic, 69.3% eosinophilic and 43.6% overlapped. There were no differences in sex or age. Allergic rhinitis was significantly more frequent in early-onset group. Eosinophils were significantly higher in late-onset patients (533 IQR 732 vs 310 IQR 410), conversely IgE levels were significantly higher in early-onset patients (342 IQR 804.5 vs 232.5 IQR 420.7). The prescription of biologics was more frequent in late-onset patients.

Conclusion: The age of onset of asthmatic symptoms is a variable of clinical relevance in the evaluation of patients with severe asthma for the decision-making to start biological therapy; prospective studies validating these findings are necessary to be able to develop best assessment and prediction models in severe asthma.