Age-related differences in the fractional exhaled nitric oxide concentration in patients with asthma

Fractional exhaled nitric oxide concentration (FeNO) is a biomarker of eosinophilic airway inflammation and a reliable predictor of corticosteroid therapy. The aim was to assess the concentration of FeNO in patients with asthma of different severity, depending on age. Methods. Our study involved 489 patients with asthma aged 4 to 68 years. 305 (62%) patients were diagnosed with asthma based on clinical symptoms and laboratory and instrumental diagnostics. The control group included 184 (38%) patients without asthma. All patients were divided into age groups: under 7 years, 8 – 10, 11 – 14, 15 – 18, 19 – 30, 31 – 55 years, and 56 years and older. FeNO level was measured according to the American Thoracic Society/European Respiratory Society recommendations using a portable hand-held nitric oxide monitor NOBreath ( Bedfont Scientific Ltd , UK). Statistical processing of quantitative data was performed using Microsoft Office Excel 2016 and Statistiсa 10.0. Results. FeNO concentration in patients with asthma was age-related. It did not exceed 35 ppb regardless of the presence of asthma and its severity in children under 7 years of age. FeNO concentration was 2 times higher in patients with asthma over 8 years of age than in the younger patients. FeNO values were comparable in the patients aged 19 – 68 years, while the range of FeNO values (M; 95% CI) in elderly people (over 55 years) was significantly wider, which may be associated with many comorbid factors and concomitant diseases. Elevated FeNO concentrations were detected 1.6 – 2 times less frequently among adult patients with mild asthma than in patients with moderate and severe asthma. The opposite trends were observed in children. Conclusion. Elevated FeNO levels in young children can serve as a sensitive biomarker reflecting changes in the respiratory mucosa.