Background and aims: Active inflammatory bowel disease (IBD) is associated with increased activity of inducible nitric oxide synthase (iNOS), which increases both mucosal and plasma nitric oxide (NO) levels. Increased fractional exhaled nitric oxide (FeNO) levels have been described in patients with IBD. Currently, hand-held FeNO measurement devices are available, enabling a fast in-office analysis of this non-invasive disease activity marker. In this pilot study, we investigated the utility of in-office FENO measurements in patients with Crohn's disease (CD).
Methods: Fifty CD patients and 25 healthy controls (HC) were included, all of whom were free of atopic or pulmonary disorders and respiratory symptoms at the time of inclusion. The Crohn's disease activity index (CDAI) was calculated, and the inflammatory parameters and fecal calprotectin levels were assessed. FeNO was measured with a hand-held device.
Results: A significant increase in FeNO (median, [interquartile range]) was observed in steroid-free CD patients with clinically active disease (CDAI > 150; 22  ppb) compared with CD patients in clinical remission (CDAI < 150; 11  ppb; P < 0.001) and HC's (17  ppb; P < 0.05). Active CD patients treated with corticosteroids had significantly lower FeNO compared with active CD patients without steroids (12  ppb vs 25  ppb; P < 0.05). FeNO displayed a strong correlation with the CDAI (R = 0.68; P < 0.001). Fair correlations were found between FeNO and several systemic inflammatory markers, but no significant correlation was found with fecal calprotectin.
Conclusion: This pilot study suggests that hand-held FeNO measurements could be an attractive non-invasive indicator of systemic inflammation in Crohn's disease.