Fractional exhaled nitric oxide (FeNO) is a non-invasive test for evaluating the degree of airway inflammation and for the diagnosis, evaluation, and treatment of asthma. We attempted to measure FeNO levels in Korean children with asthma and determine its cutoff value for diagnosing asthma. We enrolled 176 children and adolescents between the ages of 5 and 18 years, who visited for the evaluation of chronic cough, shortness of breath, and wheezing. Among them, 138 patients who underwent skin prick tests or inhalation Immuno CAP (UniCAP; Pharmacia, Uppsala, Sweden) tests for allergy testing together with a pulmonary function test were included. FeNO was measured using a NIOX MINO (Aerocrine AB, Solna, Sweden) instrument according to the American Thoracic Society/European Respiratory Society (ATS/ERS) guidelines. There were 29 patients with asthma, 43 with rhinitis, and 38 with asthma and allergic rhinitis. In the asthma group, FeNO levels significantly correlated with total immunoglobulin E (r = 0.572, p < 0.001), but did not show significant correlation with pulmonary function test parameters (forced vital capacity-FVC, forced expiratory volume in one second-FEV1, FEV1/FVC) or PC20 (provocative concentration of methacholine causing a 20% fall in FEV1). The FeNO cutoff values obtained in the asthma and asthma rhinitis groups were 16.5 ppb and 18.5 ppb, respectively. Hence, we provide a FeNO cutoff value according to the presence or absence of rhinitis in pediatric patients with asthma.
Keywords: cutoff value; fractional exhaled nitric oxide; pediatric asthma.