Mast cells are key-players in allergic diseases. The main mast cell biomarker is basal serum tryptase (bST), which depends on genetic and acquired physiological and pathological determinants. However, the association between bST levels and allergic diseases remains unclear.

This transversal study aims to correlate bST levels with IgE-sensitizations and allergic morbidities among 610 teenagers of 15/16 years old from the population-based prospective PARIS birth cohort.

Among 3840 full-term healthy children born in Paris, France from 2003 to 2006, 2117 were still being followed-up at 15/16 years of age. Among them, 610 underwent health examination, measurement of the fraction of exhaled nitric oxide (FeNO), skin prick testing (SPT) and blood sampling for tryptase measurement.

In this birth cohort, bST levels followed a bimodal distribution compatible with 5% hereditary alpha-tryptasemia. Circulating bST was positively associated with body weight, age, and male gender, and negatively with history of active tabagism. Higher bST levels were associated with higher SPT sensitization rates, spanning from 41 to 53% between the lower and the higher bST terciles. This association appeared specific for certain allergens, including grass (P=0.02), and mugwort pollen (P=0.002), and to a lesser extent for birch pollen (P=0.053), cat dander (P=0.06), and hen egg (P=0.057). In addition, bST levels were positively correlated with FeNO (P=0.01). Tryptase levels were positively associated with history of doctor-diagnosed drug reactions (P=0.03) and, among subjects sensitized to bST-associated inhaled allergens, with concomitant asthma (P=0.02), ranging from 7% (4/52) to 24% (19/78) between the lower and the higher bST terciles.

Among 610 teenagers of 15/16 years from the PARIS birth cohort, bST levels were positively associated with SPT sensitization to several pneumallergens, FeNO levels, history of drug reactions, and actual asthma in individuals sensitized to bST-associated pneumallergens. Forthcoming studies will clarify the predictive potential of bST regarding sensitization and hypersensitivity manifestations, and the role played by tryptase genotypes in allergic phenotypes.