Fraction of exhaled nitric oxide measurement as a biomarker in asthma and COPD compared with local and systemic inflammatory markers

Background: Asthma and COPD are characterized by chronic airway inflammation that results in chronic airway obstruction which is reversible in asthma and non-reversible or partially reversible in COPD. The differential diagnosis between reversible or irreversible airflow obstruction due to asthma or COPD is important in clinical practice because the prognosis and the response to treatment of the two diseases are different. Nitric oxide (NO) is produced by many cells within the respiratory tract. Endogenous NO may play an important signaling role in the physiological control of airway function and in the pathophysiology of airway diseases. Measurement of airway inflammation by means of FENO may be useful and convenient for asthma diagnosis, particularly when bronchial challenges and/or spirometric maneuvers cannot be correctly performed. The increase in the percentage of peripheral blood and sputum eosinophils was found in patients with asthma that correlated with the clinical severity of asthma and pulmonary function. Elevated levels of C-reactive protein (CRP) are established in COPD but, in asthma, the results have been inconsistent. The aim of the present study was to evaluate differences in local (airway) and systemic inflammatory markers among primary care patients with asthma and COPD using simple, rapid and easy to do tests. Subjects and methods: One hundred and fifty patients and thirty control subjects were included in this study. They were divided into three groups, ninety asthmatic patients diagnosed clinically and physiologically as reversible airway obstruction (group I). Sixty COPD patients diagnosed by clinical, physiological and laboratory tests to have irreversible or partially reversible airway obstruction (group II). The third group is the control group with no airway obstruction (NAO) including thirty subjects. Pulmonary function tests, FENO, hs-CRP, blood and sputum eosinophil percentages were done to all subjects. Results: FENO was positively correlated with all inflammatory markers in the asthmatic group with highly significant differences (p ⩽ .001) and negatively correlated with age, BMI and PFTs. In the COPD group there was a positive correlation between FENO with all inflammatory markers and PFT with highly significant differences (p ⩽ .001) with sputum and blood eosinophils and not significantly correlated with hs-CRP and PFT. Conclusion: It is concluded that there are significant differences in inflammatory patterns between asthma and COPD. FENO and hs-CRP had the highest ability to discriminate between patients with asthma and COPD