LONGITUDINAL MEASUREMENT OF AIRWAY HYPERRESPONSIVENESS IN SELECTED SUBJECTS WITH PERSISTING PULMONARY SYMPTOMS

The relationship between airway hyperresponsiveness and pulmonary symp toms was examined longitudinally in 52 subjects. Subjects were part of a larger study, the Natural History of Asthma, and had repeated measu res of airway hyperresponsiveness using methacholine. Atopy was determ ined using skin tests and serum IgE levels. The subjects completed a s tandardized respiratory questionnaire. Each subject reported respirato ry and pulmonary symptoms at either their initial or follow-up visit. The subjects did not, however, have a physician-confirmed diagnosis of asthma. Subjects were divided into groups according to the current st atus of their respiratory symptoms. The four groups included subjects who were initially normal but developed respiratory symptoms at follow -up; subjects who had symptoms at all visits; subjects with respirator y symptoms at their initial visit but who had no symptoms at follow-up ; and subjects who had respiratory symptoms prior to their initial vis it and who did not have a recurrence during follow-up. There was no st atistical difference in airway hyperresponsiveness, IgE, or skin test scores at the initial visits. Subjects who had airway responsiveness w ere significantly more atopic than subjects who did not have airway re sponsiveness. Subjects were classified as ''consistently positive:'' ' 'variable,'' or ''consistently negative'' responders according to the pattern of methacholine-induced airway hyperresponsiveness. Overall, a mong the four groups, 33% were consistently positive at all visits, 43 % were variable, and 22% were consistently negative. Airway hyperrespo nsiveness was statistically associated with atopy, but not necessarily associated with questionnaire-based respiratory symptomatology. These factors need to be considered in epidemiological studies of asthma ut ilizing respiratory questionnaires.