Exercise-Induced Asthma Diagnosis

Diagnostic Approach

The American Thoracic Society and European Respiratory Society suggest that a standardized exercise challenge test is the most appropriate test to confirm exercise-induced asthma in patients with normal baseline pulmonary function tests 1, 2
Patients with episodic shortness of breath and chest tightness during exercise, along with normal baseline pulmonary function tests, are highly suggestive of exercise-induced asthma 3
A flattened inspiratory flow loop on pulmonary function testing suggests upper airway involvement but is not diagnostic of exercise-induced asthma by itself 2

Exercise challenge testing should be performed using a treadmill or bicycle ergometer with exercise intensity sufficient to achieve 85-95% of maximum heart rate 4
The test should last for 6-8 minutes after 2-4 minutes of ramping up, with measurement of FEV1 before exercise and at 1, 3, 5, 7, 10, 15, and 20 minutes post-exercise 2, 4
A fall in FEV1 of >10% from baseline is considered positive for exercise-induced asthma 5, 6

The exercise should be performed in a temperature-controlled room (20-22°C) with relative humidity <40% to maximize sensitivity 3
Short-acting bronchodilators should be withheld for 6 hours, long-acting bronchodilators for 24 hours, and no steroids or caffeine on the day of testing 2

The European Respiratory Society suggests that Eucapnic Voluntary Hyperpnea (EVH) test can be considered as an alternative to exercise challenge testing 1, 5
Methacholine challenge can be considered if exercise challenge is not feasible, with a PC₂₀ value of ≤8 mg/mL considered positive 5, 7

The American College of Allergy, Asthma, and Immunology recommends considering differential diagnoses such as vocal cord dysfunction, exercise-induced laryngeal dysfunction, cardiac causes of dyspnea, and deconditioning 4, 8, 9
Normal baseline spirometry does not exclude exercise-induced asthma, and self-reported symptoms have poor correlation with objective findings 5, 10
Continuous pulse oximetry should be used during testing for safety, and bronchodilators should be readily available to reverse severe bronchospasm if it occurs 2