Biomarkers are essential to determine different phenotypes of childhood asthma, and
for the prediction of response to treatments. In young preschool children with asthma,
aeroallergen sensitization, and blood eosinophil count of 300/µL or greater may identify
those who can benefit from the daily use of inhaled corticosteroids (ICS). We propose
that every preschool child who is considered for ICS treatment should have these two
features measured as a minimum before a decision is made on the commencement
of long-term preventive treatment. In practice, IgE-mediated sensitization should be
considered as a quantifiable variable, i.e., we should use the titer of sIgE antibodies or
the size of skin prick test response. A number of other blood biomarkers may prove
useful (e.g., allergen-specific IgG/IgE antibody ratios amongst sensitized individuals,
component-resolved diagnostics which measures sIgE response to a large number of
allergenic molecules, assessment of immune responses to viruses, level of serum CC16,
etc.), but it remains unclear whether these can be translated into clinically useful tests.
Going forward, a more integrated approach which takes into account multiple domains
of asthma, from the pattern of symptoms and blood biomarkers to genetic risk and
lung function measures, is needed if we are to move toward a stratified approach to
asthma management.