Comparison between exhaled nitric oxide and bronchial challenge with methacholine or adenosine-5'-monophosphate in the diagnosis of childhood asthma

ABSTRACT

PURPOSE: Asthma is a chronic airway inflammatory disease characterized by bronchial hyperresponsiveness and reversible airway obstruction. Bronchial challenge with methacholine or adenosine-5'-monophosphate (AMP) has been used to diagnose asthma. Recently, measurement of exhaled nitric oxide (eNO) can also be used for the diagnosis of asthma. The aim of this study was to compare the diagnostic value for asthma between challenge with methacholine or AMP and eNO in children with chronic nonspecific respiratory symptoms. METHODS: One hundred thirty-three children who have chronic nonspecific respiratory symptoms were enrolled. Bronchial challenge with methacholin and AMP were performed, and eNO was measured in all subjects. Subjects were defined as asthma based on the clinical symptoms and bronchodilator response during follow-up of at least 3 months after test. RESULTS: Thirty-three subjects (34%) were finally diagnosed as asthma among 97 patients after 3-month follow-up. The area under the receiver operating characteristic curves for the diagnosis of asthma were 0.903 (95% confidence interval [CI], 0.838-0.969; P<0.001) for methacholline challenge, 0.867 (95% CI, 0.783-0.950; P<0.001) for AMP challenge, and 0.588 (95% CI, 0.467-0.709, P=0.156) for eNO measurement. The cutoff values of these tests were methacholine PC20 (provocative concentration of methacholine causing a 20% fall in forced expiratory volume in one second) 12.0 mg/mL (sensitivity, 87.9%; specificity, 82.8%), AMP PC20 566.2 mg/mL (sensitivity, 84.8%; specificity, 85.9%), and eNO 18.5 ppb (sensitivity, 45.5%; specificity, 71.9%). CONCLUSION: Measurement of eNO may be inferior to challenge with methacholine and AMP for the diagnosis of asthma in children.