Diagnosing Asthma With Clinically Accessible, Non-invasive, and Efficient Tests: a Child-inclusive Translational Investigation

Asthma is a common inflammatory respiratory disease affecting 11% of Canadians, but its diagnosis remains challenging, leading to delays in treatment or overtreatment. Spirometry with a reversibility test and bronchial provocation testing (BPT), considered the gold standard, are the reference diagnostic methods. However, access to BPT is limited as it is performed in hospital settings. Type 2 inflammation biomarkers, the fractional exhaled nitric oxide (FeNO) and blood eosinophils (EOS), represent a potential alternative. In addition to their prognostic and theragnostic value, these markers predict a good response to inhaled corticosteroids in individuals aged ≥ 6 years with asthma. However, their use remains restricted to pulmonologists in specialized clinics and is not recommended as a diagnostic tool in Quebec. Despite studies demonstrating their diagnostic value in specialized settings, these tests remain underexplored in primary care and insufficiently studied in children under 12 years. The objective of ou study is to evaluate the relevance and performance of FeNO and blood eosinophils in the diagnosis of asthma in children referred in primary care with non-diagnostic spirometry.