Assessment of airway inflammation in asthmatic children by measuring nitric oxide derivatives in induced sputum versus blood

ABSTRACT

Nitric oxide [NO] plays an important role in inflammation involving the airways. In this study, the concentration of NO metabolites, nitrite and nitrate, were measured in induced sputum and compared with serum in 18 children with bronchial asthma and 10 normal children. The study was done on the asthmatic children attending the outpatient clinics of the Pediatric and Chest Departments of Tanta University Hospital. Asthmatic children had ages ranging from 10-15 years. They had significantly higher NO metabolites than control subjects, in induced sputum [1082.44 +/- 86.72 micro mol/l vs. 552.00 +/- 37.34 micro mol/l, P<0.01] but not in serum. The area under the curve [AUC] revealed that the level of NO metabolites in induced sputum [0.78] was more sensitive and specific than the determination of serum NO metabolites [0.53] in differentiation of children with asthma from control subjects. In induced sputum, IL-5 was detected more frequently in children with asthma than in control subjects [15/18 [83%] vs. 1/10 [10%], [P<0.01]]. Asthmatic children had a significantly higher eosinophilic cationic protein [ECP] concentration in induced sputum compared with controls [617.89 +/- 172.78 ng/ml vs. 155.50 +/- 30.31 ng/ml, P<0.01], Serum ECP levels reached significantly higher levels in asthmatic children [691.15 +/- 71.31 ng/ml] than in controls [114.20 +/- 18.45 ng/ml] [P<0.01]. In induced sputum, eosinophils and neutrophils were significantly higher in asthmatics than controls [eosinophils 32.50 +/- 6.69% vs. 1.9 +/- 0.22%, P<0.01; neutrophils 17.5 +/- 2.5% vs. 8.4 +/- 1.6%, P<0.01], whereas the proportion of macrophages was lower in asthmatics [24.9 +/- 6.1% vs. 85.0 +/- 1.5%, P<0.01]. The level of NO metabolites in induced sputum showed significant negative correlation with the degree of airflow obstruction [FEV[1] /FVC%]; [r=-0.73, P=0.001] and positive correlation with ECP in induced sputum [r=0.61, P=0.007]. Nitric Oxide [NO] metabolites in induced sputum positively correlated with the percentage of eosinophils in sputum [r=0.62, P=0.006]. The percentages of shedded epithelial cells in sputum, used to express NO-related cellular toxicity, significantly correlated with the concentration of NO derivatives in induced sputum [r=0.71, P<0.01]. No significant correlation was found between the degree of bronchial hyperreactivity to methacholine and the level of NO metabolites in induced sputum. From this study, it can be concluded that measuring NO metabolites levels in induced sputum is a more valuable marker to assess allergic inflammation of the airways in asthmatic children than measuring NO metabolites in serum