The Use of Exhaled Nitric Oxide in the Diagnosis of Asthma in School Children

Objectives

To evaluate the yield of the fractional exhaled nitric oxide (FeNO) in the diagnosis of asthma compared with spirometry and induced sputum cytologic study in school-age children.

Study design

Consecutive children referred for evaluation of possible asthma were included. At referral, all children completed FeNO measurement, sputum induction for eosinophil count (eos%) and spirometry. The diagnosis of asthma was performed after 18 months with conventional criteria. Receiver operating curves were used to determine cutoff points for disease status, and accuracy was calculated.

Results

A total of 150 children were included: 69 with steroid-naïve asthma, 44 without asthma, and 37 with asthma treated with controllers. FeNO and eos% levels were significantly higher in those with steroid-naïve asthma (P < .0001). The area under the receiver operating curve for FeNO and eos% were very high compared with forced expiratory volume in 1second (0.906, 0.921, 0.606, respectively). The sensitivity, specificity, and positive and negative predictive values for best cutoff points of FeNO (19 parts per billion) were 80%, 92%, 89%, and 86%, respectively, and were similar to eos% (best cutoff = 2.7%): 81%, 92%, 89%, 85%, respectively.

Conclusions

FeNO measurement is useful in early diagnosis of pediatric asthma. We suggest considering FeNO measurement in the evaluation of children suspected of having asthma, especially in cases where the diagnosis is not clear.

AUC, Area under the receiver operating curve, eos%, Percentage of eosinophils, FeNO, Fractional exhaled nitric oxide, FEV₁, Forced expiratory volume in 1 second, ICS, Inhaled corticosteroid, NPV, Negative predictive value, ppb, Parts per billion, PPV, Positive predictive value, ROC, Receiver operating curve