Airway Hyperresponsiveness: A Comparative Study of Methacholine and Exercise Challenges in Seasonal Allergic Rhinitis with or without Asthma 

Background. Asymptomatic airway hyperreactivity in allergic rhinitis is a risk factor for later development of asthma. Although non-specific bronchial hyperresponsiveness (BHR) has been measured by several stimuli, the most appropriate measurement technique still remains unclear. Objective. To investigate whether an exercise challenge can be used to predict BHR in seasonal allergic rhinitis patients with or without asthma and to compare this bronchial reactivity with a methacholine challenge technique. Methods. Forty-six consecutive patients with seasonal allergic rhinitis only (n = 31) and with both seasonal allergic rhinitis and asthma (n = 15) were included in the study during the pollination period. Subjects underwent first methacholine (mch) and then exercise challenge testing (ECT). There was a 1-week interval between the tests. ECT was performed on a bicycle ergometer. Positive result was defined as a 15% decrease in forced expiratory volume in 1 second (FEV₁) post-exercise. A patient's bronchial reactivity to methacholine was considered as hyperresponsive if PC₂₀ was less than 8 mg/mL. Results. Mch PC₂₀ values were significantly lower in patients with both rhinitis and asthma (p < 0.062). Among the 46 patients, mch PC₂₀ values were significantly different between patients who had positive and negative exercise challenge tests (p = 0.007). All patients with rhinitis alone had a negative ECT and 10 had a positive mch challenge. Change in FEV₁ values after ECT was significantly higher in patients with both rhinitis and asthma compared to those with rhinitis alone (p = 0.009). There was a significant relation between positivity of mch and exercise challenges (p = 0.025). ECT positivity was found to be a significant confounding factor in the diagnosis of asthma (p = 0.001). Specificity and sensitivity values were 100% and 24% for ECT and 68% and 100% for mch, respectively. Conclusion. Exercise challenge presents poor diagnostic value for detecting bronchial responsiveness in individuals with allergic rhinitis alone during the pollen season.