Bronchial responsiveness in children and adolescents: a comparison between previously asthmatic, currently asthmatic, and normal subjects

The aim of this study was to examine the degree of bronchial responsiveness in previously asthmatic subjects. Of 253 patients, born within 1964-1974, followed in the pediatric department at the University hospital in Copenhagen, 224 subjects (89%) were successfully contacted by telephone; of these 195 complained of persistent asthma and 29 (13%) had had no asthmatic symptoms for at least 2 years. On the basis of the degree of respiratory symptoms, 58 individuals were examined at the outpatient clinic. Of these, (1) 19 were previously asthmatics, (2) 20 had current mild asthma, and (3) 19 had current severe asthma. Furthermore, 19 healthy individuals, age-matched with the preceding asthmatic subjects, were selected as controls. In all subjects, skin prick tests, lung function tests, and bronchial challenge tests with inhaled histamine and bronchodilator were performed. Furthermore, the subjects measured their peak expiratory flow (PEF) twice daily during a period of 4 weeks. Of the 39 current asthmatic subjects, 82% had a PC20 < or = 8 mg/ml, whereas all previously asthmatic subjects and the controls had a PC20 > 8 mg/ml. The degree of bronchial responsiveness as indicated by the dose-response slope (DRS), the percentage change in forced expiratory volume in 1 sec (FEV1) per inhaled mumol of histamine, was found to be significantly higher in previously asthmatic patients (median logDRS 0.1 delta %FEV1/mumol) than in controls (median logDRS-0.4 delta %FEV1/mumol) (p < 0.001). Furthermore previously asthmatic subjects had significantly increased change in FEV1 after inhalation of bronchodilator and peak expiratory flow variability compared to controls. These findings suggest that apparently asymptomatic previously asthmatic subjects have increased airway variability.