Bronchial hyper-responsiveness in children.

Bronchial hyper-responsiveness is a cardinal feature of asthma in children, but is also present in children with some other types of chronic lung disease. Techniques are now available that enable bronchial reactivity to be measured in children of almost all ages. The responses of normal and asthmatic children to standardized challenges have been measured and the optimal cut-off values separating the normal and asthmatic response have been established statistically. All types of challenge can distinguish between the child who is normal and one with lung disease within the limits of the sensitivity and specificity of the test. However, only indirect challenges, such as those by exercise or the inhalation of adenosine 5'-monophosphate, distinguish between asthma and other types of lung disease.