Bronchodilator Responses after Methacholine and Adenosine 5′-Monophosphate (AMP) Challenges in Children with Asthma: Their Relationships with Eosinophil Markers

Abstract

Background. Bronchodilator responsiveness (BDR) and eosinophilic inflammation are characteristic features of asthma. Objective. The aim of this study was to compare the relationships of BDR after methacholine challenge or adenosine 5′-monophosphate (AMP) challenge to blood eosinophil markers in children with asthma. Methods. Methacholine and AMP challenges were performed on 69 children with mild intermittent to moderate persistent asthma. BDR was calculated as the change in forced expiratory volume in 1 second, expressed as percentage change of the value immediately after the each challenge and the value after inhalation of salbutamol. Serum total IgE levels, blood eosinophil counts, and serum eosinophil cationic protein (ECP) levels were determined for each subject. Results. A positive relationship between serum total IgE levels and BDR was found only after the AMP challenge (R² = 0.345, p = .001) rather than after the methacholine challenge (R² = 0.007, p = .495). Peripheral blood eosinophil counts correlated more significantly with BDR after AMP challenge (R² = 0.212, p = .001) than BDR after methacholine challenge (R² = 0.002, p = .724). Both BDR after methacholine challenge (R² = 0.063, p = .038) and BDR after AMP challenge (R² = 0.192, p = .001) were significantly correlated with serum ECP levels. Conclusion. BDR after AMP challenge may be more closely related to eosinophilic inflammation, compared with that after methacholine challenge.

• asthma
• bronchial provocation
• bronchodilator response
• child
• eosinophils

Acknowledgment

This study was supported in part by Korea University Grant (K0933151) and Grant for the Environmental Health Center for Childhood Asthma (2010–2011), Ministry of Environment, Republic of Korea.

Declaration of Interest

The authors declare no conflicts of interest. The authors alone are responsible for the content and writing of this paper.