Airway inflammation in symptomatic and asymptomatic children with methacholine hyperresponsiveness

A definition of asthma includes symptoms due to reversible airflow limitation and airway hyperresponsiveness. Characteristically, there is also airway inflammation. In children with methacholine airway hyperresponsiveness but no asthma symptoms, we examined whether there were features of asthmatic airway inflammation. Forty one children, aged 11-16 yrs, were studied. Thirteen asymptomatic children with methacholine airway hyperresponsiveness (provocative concentration producing a 20% fall in forced expiratory volume in one second (PC20) geometric mean of 3.35 (range 1.08-7.81) mg.ml-1) were compared with 13 currently symptomatic asthmatics with a similar PC20 of 1.91 (0.42-6.5) mg.ml-1 and 13 normal children with a normal PC20 of 52.4 (17.6 to > 64) mg.ml-1. Breathlessness experienced during a methacholine test was recognized to have occurred previously in 7 out of 13 asymptomatic children and all symptomatic children. Asymptomatic children had significantly more airway responses to hyperventilation with cold dry air (4 out of 13) than normal children (0 out of 13) but less than symptomatic children (11 out of 15). Sputum induced with hypertonic saline contained lower eosinophil counts in the asymptomatic children (median (interquartile range) 0.20 (0.59)%) than in the symptomatic children (1.70 (9.45)%), and not different from the normal children (0.15 (0.61)%). Budesonide, 400 micrograms b.i.d. improved respiratory symptoms, forced expiratory volume in one second (FEV1) and methacholine PC20 in symptomatic children, but this effect did not reach statistical significance in asymptomatic children. We conclude that symptomatic children are more likely to have evidence of asthmatic inflammation than asymptomatic children and this probably explains the symptom difference.(ABSTRACT TRUNCATED AT 250 WORDS)