Airway responsiveness and atopy in families of patients with asthma.

OBJECTIVE

To determine whether there is an increased prevalence and degree of airway hyperresponsiveness (AHR) and atopy in families of patients with asthma.

DESIGN

Case-control study.

SETTING

Asthma clinic and surrounding community.

PATIENTS

A group of 28 families (n = 122) with one member who had attended the asthma clinic and a control group of 28 families (n = 122) from the same community.

INTERVENTIONS

Each family member completed a questionnaire and underwent expiratory flow measurement, skin prick tests for allergies, methacholine tests and measurement of total serum IgE level and blood eosinophil count.

OUTCOME MEASURES

Presence of atopy and AHR and relations between asymptomatic AHR or asthma and atopy, serum IgE levels or blood eosinophil counts.

RESULTS

The group of families with a member with asthma had an increased prevalence of atopy and AHR, lower PC20 methacholine and higher serum IgE levels in comparison with controls, even when the first identified family members with asthma and their matched controls were not included. The subjects with atopy in the group with a patient with asthma had higher atopic indices and serum IgE levels than those in the control group, in whom asymptomatic AHR was less closely related to atopy. There was a significant correlation between PC20 methacholine level and atopic index, between blood eosinophil count and serum IgE level, and between atopic index and serum IgE level, for all groups. The proportion of women with asymptomatic AHR was almost twice as high as that of men.

CONCLUSION

First-degree relatives of subjects with asthma have a higher prevalence of AHR, atopy and elevated serum IgE levels than controls from nonasthmatic families. Subjects with atopy in families of patients with asthma have higher atopic indices and degree of AHR than controls with atopy.