Background: Basal serum tryptase (bST) is the main marker of the mast cell compartment. In spite of the importance of mast cells regarding allergic manifestations, the relationship between bST and allergy-related outcomes has been seldomly described, particularly during early life. In addition, circulating tryptase concentrations depend of mast cell load, genetic determinants, and several physiological, pathological, and exposure factors. This study aimed to assess the potential association between bST and allergy-related outcomes in teenagers from a birth cohort. Methods: This cross-sectional study included 610 teenagers at 15/16 years participating to a French ongoing population-based prospective birth cohort. Participants answered to self-administered questionnaires, received a health check-up and blood sampling. Considered allergy-related outcomes consisted of sensitization by skin prick test and specific IgE measurements, fraction of exhaled NO measurements, and standardized diagnosis of allergy-related morbidities. Results: At 15 years , higher bST was associated with higher prevalence of sensitization to inhalants and foods. Furthermore, bST was positively associated with intermediate-to-high FeNO levels, even after adjustments for covariates including sensitization and eosinophils. After controlling for potential confounders, higher bST was also associated to higher risk of displaying any hypersensitivity reactions, reactions to drugs, and to asthma with associated sensitization. Furthermore, higher bST was associated with poorer control scores among sensitization-associated asthma. Conversely, higher bST was associated with lower risk of presenting dermatitis without associated sensitization. Conclusion: In teenagers from a birth cohort, higher bST was associated with more frequent sensitization, intermediate-to-high FeNO values, and allergy-related morbidities, including asthma.

Background : Several major sensitization profiles have been described in children with asthma, but it remains unclear how these profiles relate to asthma phenotypes. The aim of this study was to determine allergenic sensitization profiles in a megacity cohort (SAMP). Methods : This was a cross-sectional analysis performed from 2011 to 2015 including preschool and school-age children with severe and moderate asthma from the SAMP cohort. We performed ALEX multiplex array and carried out cluster analysis. Results: Data from 367 children were analysed: 224 of preschool age and 143 of school age, respectively 84 (38%) and 114 (80%) presented at least one allergic sensitization. At preschool age, three clusters were identified: Cluster 1, Few sensitizations to inhaled allergen molecular families and non-type 2 (T2) inflammation (n=61); Cluster 2, Predominant sensitization to HDM molecular families. (n=16); Cluster 3, Severe asthma with multiple sensitizations to inhaled and food allergen molecular families (n=7). At school age, five clusters were identified: Cluster 1, Few sensitizations to inhaled allergen molecular families and non-T2 inflammation (n=43); Cluster 2, Predominant sensitization to HDM molecular families (n=31); Cluster 3, Predominant sensitization to PR-10 family (n=25); Cluster 4, Severe asthma with predominant sensitization to tropomyosin family (n=11); Cluster 5, Severe asthma with multiple sensitizations to inhaled and food allergen molecular families (n=4). Conclusion: These results underline the heterogeneity of sensitization profiles in severe allergic childhood asthma. The most severe asthma phenotypes were associated with multiple sensitizations to both inhaled and food allergen molecular families as expected, and to the tropomyosin molecular family, a novel finding.