Interrelationships among asthma, atopy, rhinitis and exhaled nitric oxide in a population-based sample of children

Exhaled nitric oxide (eNO) has attracted increasing interest as a non-invasive marker of airway inflammation in asthma. However, little evidence exists on the influences exerted on eNO by the interrelations among atopic status, asthma and rhinitis.

Among the 1156 children who participated in a large-scale epidemiological survey on asthma and allergies (ISAAC II: International Study of Asthma and Allergies in Childhood Phase II) in the city of Clermont-Ferrand, 53 asthmatics without corticosteroid treatment and 96 non-asthmatics were invited to perform eNO and skin prick tests (SPTs) to 12 common allergens.

Atopic asthmatic children had higher eNO than non-atopic asthmatic children (28.9+/-9.1 vs. 17.1+/-13.1 p.p.b.; P=0.0004) with a significant increase when one SPT or more are positive (26.5+/-7.8 vs. 17.1+/-13.1 p.p.b.; P=0.03). Similarly, non-asthmatic, atopic subjects had higher eNO than non-atopic subjects with a significant increase when two SPTs or more are positive (19.4+/-9.8 vs. 11.7 +/-6.7 p.p.b.; P=0.003). In the case of equal levels of positive SPTs (0, 1, >/=2), asthmatic children always had higher eNO than non-asthmatic ones. Furthermore, among non-asthmatic children, the eNO level increased only in atopics who had rhinitis (20.7+/-13 vs. 12.5+/-6.4 p.p.b. in atopic controls (subjects without rhinitis and asthma) and 12.3+/-6.6 p.p.b. in non-atopic controls; P=0.001), whereas among asthmatic children, eNO level increased in atopics independently of rhinitis (28.2+/-9.5 p.p.b. in those with rhinitis and 30.9+/-8.1 p.p.b. in those without) as well as in non-atopics with rhinitis (22.5+/-17.2 p.p.b.).

Our data suggest that besides atopy and asthma, allergic rhinitis should also be taken into account in the assessment of eNO.