Is exhaled nitric oxide a useful adjunctive test for assessing asthma

Rationale. To determine the general utility of clinical (Asthma Control Test) and physiologic (forced expiratory volume in the first second of exhalation [FEV1] and fractionated exhaled nitric oxide level [FeNO]) parameters for characterizing asthma patients. Methods. Two cross-sectional independent studies simultaneously enrolled 100 patients in the US and 109 patients in Spain ≥ 18 years of age with a physician-diagnosis of asthma and confirmed by a ≥ 12% improvement in FEV1 after bronchodilators or the presence of airway hyperresponsiveness, a central feature of asthma, as measured by methacholine challenge (PC20 < 10 mg/mL). There was no restriction on asthma severity or treatment. Patients were excluded if they had a diagnosis of chronic obstructive pulmonary disease and/or were current cigarette smokers. Statistical analyses were performed to compare ACT, FeNO, and spirometry within and between sites. Results. Population characteristics revealed significant differences in distributions of age, perce...