Correlations between exhaled nitric oxide levels, blood eosinophilia, and airway obstruction reversibility in childhood asthma are detectable only in atopic individuals

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Abstract
The aim of this study was to compare in atopic and nonatopic asthmatic children correlations between two inflammation parameters, i.e., blood eosinophilia and exhaled nitric oxide (FENO), and pulmonary function values, at baseline and after β2‐adrenergic bronchodilators. Ninety‐two steroid‐naive asthmatic children were evaluated: 26 were skin prick test‐ and RAST‐negative (nonatopic subjects), whereas 66 were atopic, 15 being sensitized only to house dust mites (monosensitized) and 51 to mites and to at least one other class of allergens (polysensitized). Baseline spirometric values (FEV1 and FEF25–75%) were similar in atopic and nonatopic groups (P > 0.1, each comparison). However, when compared to nonatopic subjects, atopic children showed a significantly higher degree of blood eosinophilia (3.0% and 6.7% white blood cell count, respectively; P = 0.0001) and higher FENO levels (6.8 ppb and 16.0 ppb, respectively; P = 0.0001). While a positive correlation between FENO levels and blood eosinophilia was observed in atopic children (r = 0.25, P = 0.041), no correlations between these two inflammation parameters and baseline pulmonary function values were demonstrated in any of the asthmatic groups. Inhalation of a β2‐agonist drug induced in the two asthmatic populations similar improvements in FEV1 and FEF25–75% and no changes in FENO levels or blood eosinophilia. However, only in atopic children positive correlations were found between percent variation in FEV1 (Δ%FEV1) and FENO levels (r = 0.35, P = 0.006) or blood eosinophilia (r = 0.26, P = 0.04). Within the atopic group, no differences were found between mono‐ and polysensitized individuals in all parameters evaluated. Thus only in atopic children did parameters of inflammation correlate with airway obstruction reversibility. Pediatr Pulmonol. 2003; 35:358–363.