Exhaled nitric oxide and its relationship to airway responsiveness and atopy in asthma

Exhaled nitric oxide (NO) has attracted increasing interest as a non-invasi ve marker of airway inflammation. The purpose of this study was to determin e whether exhaled nitric oxide in subjects with asthma varied according to their atopic status and to examine its correlation with airway hyperrespons iveness and lung function measurements. Forty patients with asthma and 13 controls participated in the study. Nitri c oxide was measured on three occasions with intervals of at least 3 days, using a chemiluminescence method. Airway responsiveness was assessed with m ethacholine challenge and lung function measurements were made. All subject s recorded peak expiratory flow and kept a symptom diary during a 17-day pe riod. There was no significant difference in lung function measurements, pe ak expiratory flow or symptom score between the two asthma groups. Atopic p atients with asthma had a significantly higher mean amount of exhaled NO th an non-atopic subjects with asthma (162+/-68 vs. 113+/-55 nl min(-1); P = 0 .03) and the control group (88+/-52 nl min(-1); P = 0.004). No significant difference was found in the amount of exhaled NO between non-atopic patient s with asthma and the controls. In atopic subjects with asthma the mean exh aled NO was significantly correlated to the dose-response slope for methach oline (r = -0.52; P = 0.02), while no such correlation was found in the non -atopic group. In conclusion; in this study, atopic subjects with asthma had higher levels of exhaled NO than non-atopic subjects. Atopic status should be taken into account when measuring levels of exhaled NO in subjects with asthma. (C) 1 999 Harcourt Publishers Ltd.