D2.488 - Functional confirmation of exercise-induced bronchoconstriction in children: A three-year retrospective study

Exercise-induced bronchoconstriction (EIB) is frequently suspected in children based on exercise-related respiratory symptoms, although functional confirmation is not always performed. We aimed to review specific exercise challenge tests in a paediatric population and to explore clinical and functional patterns associated with bronchoconstrictive response.

We conducted a three-year retrospective study including children referred to a tertiary centre for treadmill exercise challenge testing due to suspected EIB. Demographic data and baseline lung function (FEV₁, FVC, FEV₁/FVC, FEF_25-75) were collected, along with clinical variables including previous diagnosis of asthma, allergic rhinitis, aeroallergen sensitization, typical exercise-related symptoms, and prior bronchodilator use from clinical records. FEV₁ was measured at baseline and at 1, 3, 5, 10, 15, and 30 minutes post-exercise. EIB was defined as a ≥10% fall in FEV₁. Statistical analysis included chi-square tests, Mann–Whitney U test, Kruskal–Wallis test, and Spearman correlation.

Fifty-five children were analysed (mean age 12.9 ± 2.8 years); eight (14.5%) had a positive challenge. Typical exercise-related symptoms reported in clinical records were significantly associated with confirmed EIB (24% vs 0%, p=0.012), while asthma diagnosis, allergic rhinitis, aeroallergen sensitization, prior bronchodilator use, age, body-mass index, and baseline spirometric parameters were not predictive. When stratified by maximal FEV₁ fall (<5%, 5–10%, >10%), similar temporal patterns of post-exercise FEV₁ decline were observed across all strata, with a nadir occurring within the first 10 minutes after exercise. Baseline FEV₁/FVC demonstrated a moderate inverse correlation with maximal FEV₁ decline (r=−0.411, p=0.002).

In this real-world paediatric cohort, functional confirmation of EIB was uncommon despite frequent clinical suspicion, and no asymptomatic child demonstrated significant bronchoconstriction. The shared temporal pattern of FEV₁ decline across severity strata supports a graded physiological response rather than a strictly dichotomous condition defined by an arbitrary threshold. The association between lower baseline airflow ratios and greater post-exercise decline suggests that subtle baseline airflow limitation may predispose to more pronounced bronchoconstriction. Careful characterization of symptoms may improve accuracy on selecting patients for functional testing.