Exhaled nitric oxide as a marker of lung involvement in Crohn's disease

Crohn's Disease is an inflammatory bowel disease associated with a variety of systemic manifestations, including large and small airway involvement. The latter is most often a subclinical one, and requires expensive and invasive diagnostic approaches. Nitric Oxide (NO) can be detected non-invasively in the exhaled air (eNO) and be considered as a surrogate marker of airway inflammation. eNO tested at multiple expiratory flows can be used to distinguish the alveolar concentration of NO (C_alvNO) from the total amount of fractional eNO (FeNO). The aim of our study is to compare FeNO and concentration of alveolar nitric oxide (C_alvNO) levels and to assess their relationship with pulmonary involvement in Crohn's patients differing in clinical stage and therapeutic regimens versus a group of healthy subjects. Thirty Crohn's patients not showing clinical evidence of pulmonary diseases and 21 non-smoking, non-atopic healthy controls were enrolled. FeNO (14.9±10.2 ppb vs 10.1±6.3 ppb, p=0.049) and C_alvNO (4.4±2.2 ppb vs 2.6±1.9; p=0.006) values were found to be significantly higher in Crohn's patients than in healthy controls. Both FeNO and C_alvNO correlated positively with the Crohn's Disease Activity Index. In conclusion, our results for FeNO and C_alvNO confirm the presence of subclinical pulmonary involvement in Crohn's disease. eNO measurement may be of clinical value in the follow-up of Crohn's patients.