DETERMINANTS OF BRONCHIAL RESPONSIVENESS IN THE EUROPEAN-COMMUNITY RESPIRATORY HEALTH SURVEY IN ITALY - EVIDENCE OF AN INDEPENDENT ROLE OF ATOPY, TOTAL SERUM IGE LEVELS, AND ASTHMA SYMPTOMS

The aim of the analysis was to test whether total serum IgE levels, sp ecific serum IgE levels, and asthma symptoms are independent predictor s of bronchial hyperresponsiveness (BHR), after controlling for known risk factors or potential confounders. The study was carried out on a sample of 875 young adults, 20-44 years old, who took part in the Euro pean Community Respiratory Health Survey in Italy. The subjects underw ent a dose-response methacholine challenge test. We also measured airw ay caliber as the baseline FEV1, in absolute terms and as percentage o f forced vital capacity (FVC); skin wheal response to 11 common enviro nmental allergens; and total and specific serum IgE levels to mites, m olds, pets, and respiratory symptoms by means of a standardized questi onnaire. Atopy (positive skin prick test and/or positive specific IgE assay), total IgE, asthma symptoms, airway caliber, and age appeared t o be independent predictors of BHR. When all the other risk factors we re taken into account, atopy and total IgE were associated with a thre efold increase in BHR risk and thus emerged as the main determinants o f BHR. The importance of symptom status as a determinant of BHR decrea sed remarkably after controlling for atopy and IgE: the odds ratio of current asthmatics to asymptomatic subjects decreased from 15.3 to 8.8 . When controlling for symptoms and atopy, a family history of allergi c diseases and early respiratory infections was not found to be associ ated with BHR. Both FEV1 and FEV1/FEC were strongly and inversely asso ciated with BHR. When airway caliber was taken into account, older age was associated with decreased responsiveness, and the level of respon siveness did not differ significantly between males and females and be tween smokers and nonsmokers. The results from this analysis indicate that at any given age, irrespective of sex and smoking habits, total s erum IgE, specific IgE, airway caliber, and asthma symptoms are the ma in independent factors influencing the occurrence of BHR in a young ad ult sample.