Diagnostic performance of the measurement of nitric oxide in exhaled air in the diagnosis of COPD phenotypes

Abstract

IntroductionCOPD is a highly heterogeneous disease that has a serious impact on affected populations. Patients share some of the features of bronchial asthma, often summarized under the term ACOS (asthma-COPD overlap syndrome). The objective of this study is to evaluate the utility of the measurement of nitric oxide in exhaled air (FENO50) in the diagnosis of COPD phenotypes. Material and methodsThe study comprised cross-sectional observation of patients receiving assistance during a respiratory outpatient visit. Patient data was collected on lung function, FENO, questionnaires scoring CAT®(COPD Assessment Test), and COPD clinical phenotype. Results192 patients were studied: 103 with COPD; 16 healthy non-smokers; 30 healthy smokers; and 43 asthmatics. COPD patients were grouped by phenotype: 34 non exacerbators (33.0%); 22 ACOS (21.3%); 13 frequent exacerbators with emphysema (12.6%); and 34 frequent exacerbators with chronic bronchitis (33.0%). ACOS patients showed significantly higher FENO50 values compared to the others after adjustments for confounding factors. FENO50 demonstrated greater diagnostic accuracy than the bronchodilator test (BT) in the diagnosis of ACOS and COPD phenotypes (AUC 0.79 vs 0.74), with an optimal cut-off value of 19 ppb (sensitivity 0.68, specificity 0.75). ConclusionsPatients with COPD have different levels of FENO50 depending on the COPD phenotype. FENO50 measurement provides better diagnostic accuracy than BT, with an optimal cut-off value of 19 ppb.