Background Recent studies suggest that atopy may be associated with exercise-induced bronchospasm (EIB) in asthma. However, it is not clear whether atopy is related to EIB, regardless of airway hyper-responsiveness (AHR) to methacholine, because asthmatic subjects often show AHR to exercise and methacholine simultaneously.
Objective To investigate whether atopy is related to EIB in asthmatic subjects, independently of AHR to methacholine.
Methods Fifty-eight male asthmatic subjects were studied. Initial spirometry was performed. Skin prick test was carried out, using 53 common allergens including mites dust antigen. Atopy score was defined as a sum of mean weal diameters to all allergens tested. Methacholine bronchial provocation testing was performed. Twenty-four hours later, free running test was performed. Positive EIB was defined as a 15% reduction or more in FEV1 from baseline after exercise.
Results All subjects had AHR to methacholine. The degree of AHR to methacholine in asthmatics with EIB was similar to that in asthmatics without EIB. However, atopy score and skin reaction to Dermatophagoides pteronyssinus significantly increased in asthmatics with EIB compared with those without EIB (P < 0.05, respectively). Furthermore, the degree of EIB significantly correlated with atopy score in all subjects (r = 0.35, P < 0.01). This relationship was maintained even after the exclusion of EIB-negative asthmatic subjects.
Conclusion Atopy defined as skin test reactivity may contribute to the development of EIB in asthma, independently of AHR to methacholine.