Allergic sensitization, respiratory diseases and nitric oxide levels in healthy schoolchildren.

Background: Aim of the study was to investigate the relationships between allergic sensitisation, respiratory diseases and exhaled nitric oxide (eNO) levels in a sample of schoolchildren of Palermo, South Italy. Method: We studied 766 schoolchildren, aged 10-16 years, randomly selected from 16 junior high schools (360 males), aged 10-16 years. Each of them fulfilled a respiratory questionnaire and performed eNO measure (by off-line method), spirometry, and skin prick tests (SPT) for more common allergens in the Mediterranean area. Atopy was defined as at least a positive (3 mm mean wheal diameter) SPT. Prick index (PI) was computed as the sum of all positive reactions. Results: Asthmatics (doctor diagnosed asthma - A) were 91 (11.9%); rhinitics (positive answer to the question "Have you ever had sneezing, or runny, or blocked nose apart from common cold or flu in the last 12 months?" - R) were 238 (31.1%); control subjects (C) were 437 (57.0%). Atopy prevalence was 40.6% in the whole sample, and 60.4%, 42.9%, and 35.2% among A, R, and C respectively (p0.0001). Exhaled NO was (median and inter-quartile range) 19.5 ppb (12.7-35.0) among atopics and 14.0 (10.6-18.5) among non atopics (p0.0001). Natural log of eNO showed a positive linear correlation to PI (p0.0001). When eNO was used as dependent variable in a logistic model, atopy (OR 4.7, 95% CI 3.3-6.8), asthma (OR 2.2, 95% CI 1.3-3.6), and rhinitis (OR 1.5, 95% CI 1.0-2.2) were significant predictors of increased eNO, after adjustment for confounding variables. The association of asthma and atopy increased the risk for elevated eNO levels (OR 11.1, 95% CI 5.8-20.9). Conclusion: The present study points out that in children atopy is a major determinant