Background Exhaled nitric oxide is an easy noninvasive test, which is used for monitoring of different airway diseases. The aim of this study is to assess the usefulness of the fraction of exhaled nitric oxide (FeNO) in patients with chronic or recurrent coughing.

Methods In this cross-sectional case- controlled observational study; we measured the (FeNO) level among children suffering from different chronic airway diseases (Asthma and Bronchiectasis). The study was conducted on 40 patients (5 years and up, both males and females) diagnosed clinically and radiologically as bronchial asthma (n = 20) and lung bronchiectasis of different aetiology (n = 20) compared to 40 age-and sex-matched controls. FeNO was measured using NO breath^® instrument (I. D. NBR022714, Bedfont Scientific Ltd, UK). It was significantly elevated in children with asthma compared to healthy controls (p < 0.001). FeNO was significantly lower in patients with bronchiectasis compared to healthy controls (p < 0.001). FeNO levels in primary ciliary dyskinesia (PCD) (n = 3) were very low whereas the differences between congenital bronchiectasis and cystic fibrosis levels were not significant.

Conclusion The study concluded that FeNO measurement is an important diagnostic test and screening biomarker for chronic paediatric airway diseases. Although FeNO can’t differentiate between causes of bronchiectasis, It can be used as a diagnostic test in PCD as it has significantly low levels.