D3.131 - Comparative Assessment of Exercise Provocation, and Impulse Oscillometry in Young Adults With Exercise-Induced Respiratory Symptoms

Exercise-induced bronchoconstriction (EIB) is a frequent cause of exertional dyspnea and wheezing in young adults. However, diagnosis is often challenging because baseline spirometry is frequently normal and methacholine bronchial provocation testing (MBPT) does not always correlate with exercise-related symptoms. This study aimed to evaluate the diagnostic characteristics of MBPT, exercise provocation testing (EPX), spirometry, and impulse oscillometry (IOS) in young adults presenting with exercise-induced respiratory symptoms.

Twenty-five young adult male patients in their early twenties presenting with exertional dyspnea and wheezing were enrolled. All subjects underwent MBPT, EPX, baseline spirometry, bronchodilator responsiveness testing, and IOS. EPX positivity was defined according to standardized criteria. Clinical characteristics, spirometric parameters, and IOS indices were compared between EPX-positive and EPX-negative groups using Mann–Whitney U tests for continuous variables and Fisher’s exact tests for categorical variables. Logistic regression analysis was explored to identify predictors of EPX positivity.

EPX was positive in 72% of subjects, while MBPT was positive in 79%. MBPT positivity was significantly associated with EPX positivity (p = 0.006); however, discordant results were observed, including EPX-positive patients with negative MBPT. Baseline spirometric parameters, including FEV₁, FVC, and FEF₂₅-₇₅, did not differ significantly between EPX-positive and EPX-negative groups. IOS-defined small airway dysfunction tended to be more frequent in EPX-positive patients, although this did not reach statistical significance.

Among EPX-negative subjects, bronchodilator responsiveness was observed in a subset of patients, with FEV₁ and FEF₂₅–₇₅ bronchodilator responses present in 14.3% and 28.6%, respectively. While IOS-defined small airway dysfunction was uncommon in EPX-negative patients, bronchodilator responsiveness assessed by IOS was frequently detected, with positive responses in R5–R20 and AX observed in 71.4% and 57.1% of patients, respectively

In young adults with exercise-induced respiratory symptoms, MBPT alone may be insufficient for diagnosing EIB, and normal baseline spirometry does not exclude exercise-related airway dysfunction. EPX remains essential for confirming EIB, while IOS may provide complementary information by detecting airway reversibility not captured by exercise testing, particularly in EPX-negative but symptomatic patients. Larger studies are warranted to further clarify the diagnostic role of IOS in this population.