Importance of fractional exhaled nitric oxide in the differentiation of asthma–COPD overlap syndrome, asthma, and COPD

Abstract

BackgroundFractional exhaled nitric oxide (FeNO) is an easy, sensitive, reproducible, and noninvasive marker of eosinophilic airway inflammation. Accordingly, FeNO is extensively used to diagnose and manage asthma. Patients with COPD who share some of the features of asthma have a condition called asthma–COPD overlap syndrome (ACOS). The feasibility of using FeNO to differentiate ACOS patients from asthma and COPD patients remains unclear.MethodsFrom February 2013 to May 2016, patients suspected with asthma and COPD through physician’s opinion were subjected to FeNO measurement, pulmonary function test (PFT), and bronchial hyperresponsiveness or bronchodilator test. Patients were divided into asthma alone group, COPD alone group, and ACOS group according to a clinical history, PFT values, and bronchial hyperresponsiveness or bronchodilator test. Receiver operating characteristic (ROC) curves were obtained to elucidate the clinical functions of FeNO in diagnosing ACOS. The optimal operating point was also determined.ResultsA total of 689 patients were enrolled in this study: 500 had asthma, 132 had COPD, and 57 had ACOS. The FeNO value in patients with ACOS was 27 (21.5) parts per billion (ppb; median [interquartile range]), which was significantly higher than that in the COPD group (18 [11] ppb). The area under the ROC curve was estimated to be 0.783 for FeNO. Results also revealed an optimal cutoff value of >22.5 ppb FeNO for differentiating ACOS from COPD patients (sensitivity 70%, specificity 75%).ConclusionFeNO measurement is an easy, noninvasive, and sensitive method for differentiating ACOS from COPD. This technique is a new perspective for the management of COPD patients.

Current appraisal of single inhaler triple therapy in COPD

“… 24 In patients with so-called asthma COPD overlap a cutoff value of 22 ppb has been proposed. 25 It is interesting to speculate if, eg, a combination of FeNO ≥20 ppb and blood eosinophils ≥150/µL might be more predictive of identifying an ICS responsive phenotype than perhaps using eosinophils alone. Further work is needed to more clearly identify such threshold values for FeNO in COPD.…”

Clinical and inflammatory characteristics of Asthma-COPD overlap in workers with occupational asthma

“…The identification of ACO within COPD populations allowed the identification of subjects with underlying eosinophilic inflammation who may respond better to inhaled corticosteroids (ICS) than COPD subjects without ACO[ 8 , 9 ]. The relevance of the use of biomarkers such as atopy, IgE, or eosinophilia in blood or sputum has been emphasized to identify ACO subjects among populations of COPD subjects[ 10 – 12 ].…”

New asthma testing enhances the care of respiratory patients

“…While high levels indicate asthma, Chen et al found that FeNO values in patients with ACOS were also significantly higher than in those with COPD, and FeNO is therefore also useful in these patient groups. In patients with ACOS, the FeNO value was 27 ppb (vs. 18 ppb in COPD) (Chen et al, 2016). Their results also indicated an optimal cut-off value of >22.5 ppb for differentiating ACOS from COPD (sensitivity 70%; specificity 75%).…”

“…Criteria for diagnosis have mainly been established based on consensus and FeNO has been attracting the attention of clinicians in this area (Mostafavi-Pour-Manshadi et al, 2017). Chen et al (2016) emphasise the utility of FeNO for the differentiation The speed and ease of FeNO testing make it an appealing option for use in hospital of asthma, COPD, and ACOS. While high levels indicate asthma, Chen et al found that FeNO values in patients with ACOS were also significantly higher than in those with COPD, and FeNO is therefore also useful in these patient groups.…”