Utility of nitric oxide for the diagnosis of asthma in an allergy clinic population

Abstract

Fractionated exhaled nitric oxide (FeNO) expression is increased in airway inflammation and several studies have suggested that FeNO measurement can be useful in patients with asthma. Atopic individuals have increased FeNO levels, indicating that atopy may be a codeterminant in FeNO production. The aim of this study was to determine the discriminative value of FeNO for asthma and other atopic conditions in the general allergy clinic. Patients referred to the outpatient allergy clinic were screened. A standardized questionnaire was taken and atopic status was assessed (skin-prick test or specific plasma IgE). FeNO level and spirometry were measured. If the patient's history was suspect for asthma, a provocative concentration causing a 20% decrease in forced expiratory volume in 1 second (PC(20)) histamine challenge followed. One hundred fourteen steroid-naive patients were included. Forty-two subjects were diagnosed as asthmatic patients and 72 were diagnosed as nonasthmatic patients, comprising patients with allergic rhinitis (n = 32), nonallergic rhinitis (n = 11), urticaria (n = 11), eczema (n = 7), and other (n = 11). Asthmatic patients had a higher FeNO level than nonasthmatic patients (44 ppb versus 17 ppb; p < 0.001). Receiver operating characteristic curve analysis revealed the optimal FeNO level to distinguish asthma from nonasthma at 27 ppb, with a sensitivity of 78%, specificity of 92%, a positive predictive value of 86%, and a negative predictive value of 87%. Increased FeNO was positively correlated with the presence of respiratory symptoms (p < 0.01), airflow reversibility (p < 0.001), total IgE (p < 0.001), and negatively correlated with PC(20) histamine (p = 0.019). Multivariate analysis revealed that atopy was not a significant predictor of FeNO in asthmatic patients. Measuring FeNO is a simple and useful test to differentiate new asthma patients from those with other atopic conditions in a general allergy clinic.

Measurement of exhaled nitric oxide concentration in asthma: a systematic review and economic evaluation of NIOX MINO, NIOX VERO and NObreath

“…A further three studies 80,81,92 were identified from the update search. Four of these studies 70,77,87,95 included data for FeNO testing in conjunction with another test.…”

The Interpretation of Exhaled Nitric Oxide Values in Children With Asthma Depends on the Degree of Bronchoconstriction and the Levels of Asthma Severity

“…32,33 We carefully noted that, in many of the clinical studies in adults, it is advised to perform F ENO measurements before any other lung function measurement and even before usage of short-acting ␤ 2 agonists, 34,35 and the same order of measurements and procedures is followed by most of the studies in children. 19,20,36 It does not seem justified in the context of our results in children with asthma. Therefore, our results reveal important new clinical aspects regarding the order of measurements in children with asthma.…”

“…Moreover, it showed that an increased F ENO level was positively correlated with the presence of respiratory symptoms and air flow reversibility; however, in their study, all subjects were steroid naive. 19 We conducted a similar analysis, and we found a linear increasing trend of change from baseline in bronchial reversibility test using FEV 1 values across 4 F ENO categories of children with moderate asthma. In contrast with our study, in the study by Cordeiro et al, 19 the patients were not categorized into different asthma groups nor was the exact number of participants provided.…”

“…19 We conducted a similar analysis, and we found a linear increasing trend of change from baseline in bronchial reversibility test using FEV 1 values across 4 F ENO categories of children with moderate asthma. In contrast with our study, in the study by Cordeiro et al, 19 the patients were not categorized into different asthma groups nor was the exact number of participants provided. The authors of yet another study identified 4 clusters of subjects with well-controlled asthma versus uncontrolled asthma, associated with increased airway tone; F ENO did not differ in these 4 clusters.…”

“…A limited number of previous studies in children are similar to our results. 19,20 The study by Cordeiro et al 19 showed that the highest diagnostic accuracy of asthma can be achieved by the combination of F ENO (Ͼ 27 ppb) and/or the presence of bronchodilator reversibility. Moreover, it showed that an increased F ENO level was positively correlated with the presence of respiratory symptoms and air flow reversibility; however, in their study, all subjects were steroid naive.…”