Making a differential diagnosis between asthma and chronic obstructive pulmonary disease (COPD) may be as simple as breathing in and breathing out. A research duo from the Departments of Chest and Clinical & Chemical Pathology at Benha University in Egypt determined that a fraction of exhaled nitric oxide (FENO) is a reliable biomarker for discriminating between reversible airway obstruction in asthma and non-reversible/partially-reversible airway obstruction in COPD.
“FENO was positively correlated with all inflammatory markers in the asthmatic group with high significant differences,” wrote Dr. Abeer Rawy and Dr. Amira Mansour in “Fraction of Exhaled Nitric Oxide Measurement as a Biomarker in Asthma and COPD Compared with Local and Systemic Inflammatory Markers,” published in Egyptian Journal of Chest Diseases and Tuberculosis.
Nitric oxide is a natural molecule integral to many cell functions, especially those cells within the respiratory tract. It plays a large role in cell signaling pathways and controls airway function pathophysiology. In the case of asthma, nitric oxide levels are elevated due to greater production by bronchial epithelial cells. The rise in FENO can be detected in asthma patients more easily than other forms of testing for asthma, such as bronchial challenges and spirometric maneuvers.
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On the other hand, FENO is lower in patients with mild-to-moderate COPD, except in the case of hospitalization during exacerbations of COPD. Due to this difference in FENO behavior, the researchers aimed “to evaluate the difference in airway and systemic inflammatory markers among primary care patients with asthma and COPD. This might assist the differentiation between asthma and COPD in primary care.” It is important to differentiate between the two diseases because they require different means of treatment.
The study consisted of 150 patients and 30 healthy individuals over the course of one year. Patients were divided into three groups. Ninety asthma patients had reversible airway obstruction, 60 COPD patients had irreversible or partially reversible airway obstruction, and the other 30 patients had no airway obstruction. Each participant had their FENO measured using a special instrument placed over the mouth, gave samples of blood and sputum, and underwent pulmonary function tests.
Upon compiling the results, the researchers confirmed that asthmatic patients had higher FENO, which was negatively correlated to age, body mass index, and pulmonary function tests. For COPD patients, there was a positive correlation between inflammatory markers and pulmonary function tests. “It is concluded that there are significant differences in inflammatory patterns between asthma and COPD,” wrote the authors. “[FENO] had the highest ability to discriminate between patients with asthma and COPD.”