Symptoms, atopy, and bronchial reactivity after lower respiratory infection in infancy.

We studied the prevalence of subsequent respiratory symptoms and the relation between atopic status and bronchial reactivity in 200 index children and their controls 7 years after acute lower respiratory tract infections in infancy. Index children with recurrent symptoms differed from controls in respect of social and family characteristics and atopic background. Ventilatory function was diminished and bronchial reactivity increased. Symptom free index children also came from poorer environmental backgrounds, but did not otherwise differ from controls. 'Atopic' index children differed significantly from controls in respect of subsequent symptoms and ventilatory function and similar adverse trends were observed in 'non-atopic' index children. A comparable proportion of 'atopic' and 'non-atopic' index children showed bronchial reactivity (33.5% and 38.9% respectively). Index subgroups with and without bronchial reactivity had increased cough and wheeziness compared with respective matched controls. The former included children with 'established' asthma and the latter those with 'established' bronchitis. Atopic backgrounds were similar in both subgroups, with no differences between cases and controls. These findings suggest that atopic background and bronchial reactivity are not closely related but may contribute independently to the persistence of symptoms after respiratory infections in infancy. Bronchial reactivity may be a more useful basis than atopic status on which to separate children with episodic cough or wheeze, or both, into 'asthmatic' and 'bronchitic' subgroups.