METACHOLINE DOSE-RESPONSE CURVE IN 2 GROU PS OF SUBJECTS SUFFERING FROM ASTHMA OR CYSTIC-FIBROSIS

Nonspecifc bronchial hyperreactivity is a specific feature of the airw ays of asthmatic subjects, but is also observed in the course of non-a sthmatic chronic bronchitis. Given that cystic fibrosis is a chronic r espiratory disease significantly different from asthma, ve conducted t his study with the following objective: evaluation of the frequency of a positive metacholine nonspecific bronchial provocation test (NSBPT) in subjects suffering from cystic fibrosis and in asthmatics, and the dose-response curves in subjects with a positive metacholine NSBPT, i n order to more clearly understand the significance of sensitivity (PC 20-FEV1) and reactivity (PC35-FEV1, Area 35). The relationship between the parameters considered in the two groups as also identified. The a uthors studied a group of 25 asthmatic subjects between the ages of 8 and 18 years (mean: 11.9+/-2 years); a second group of 21 subjects suf fering from cystic fibrosis between the ages of 8 and 26 years (mean: 14.3+/-8 years); a third group of 10 normal subjects, between the ages of 8 ans 14 years (mean: 11.2+/-1.8 years), constituted the control g roup. In the 25 asthmatic subjects, 21 (84%) had a positive NSBPT: the PC20-FEV1 and PC35-FEV1 were calculated. In 21 cystic fibrosis subjec ts, 12 (57%) had a positive NSBPT, hut the PC35-FEV1 could be calculat ed in only two of them, as the PC35-FEV1 could not be reached in the o ther 10 subjects despite the administration of the maximum dose of met acholine. The mean value of PC20-FEV1 was 1.53+/-0.5 mg/mL of metachol ine in asthma (''moderate'' sensitivity) and 5.01+/-1.2 mg/mL in cysti c fibrosis (''slight'' sensitivity) p <0.02. Mean values for Area 35 w ere 217.06+/-51.4 and 760.93+/-93 in asthmatics and subjects suffering from cystic fibrosis, respectively (P <0.0001); asthmatic patients th erefore presented a ''severe'' reactivity, while the cystic fibrosis p atients presented ''moderate'' reactivity. In conclusion, metacholine NSBPT with evaluation of the slope of the dose-response curve and ther efore the sensitivity (PC20-FEV1) and reactivity (PC35-FEV1, Area 35), is therefore a useful method to distinguish subjects suffering from a sthma from those suffering from non-asthmatic bronchitis.