Bronchial reactivity in cystic fibrosis.

There is considerable dispute regarding the prevalence of asthma in patients with 
cystic fibrosis (CF). We studied 50 patients with CF and compared 
their responsiveness to inhaled histamine with that of asthmatic children. The 
incidence of positive responses to inhaled histamine was 24% in the 
patients with CF and more than 90% in the asthmatic patients. 
We found no correlation, in the patients with CF, between the 
histamine response and several indexes of atopy (clinical allergic disease and 
positive allergen skin tests). Positive responders to histamine were not evenly 
distributed over the disease spectrum of CF. Instead, positive responses occurred 
only in those patients whose prechallenge pulmonary function was abnormal. We 
conclude that the heightened bronchial reactivity in patients with CF reflects 
the severity of their underlying lung disease rather than the presence 
of coexistent asthma. 