The relationship between the severity of inflammatory bowel diseases and expirium air carbon monoxide levels.

Introduction: We investigated the relationship between expirium air carbon monoxide (E-CO) levels and disease severity in patients with ulcerative colitis (UC) and Crohn's disease (CD).

Methods: After their first follow-ups, the E-CO levels of 162 patients with UC and 100 with CD were measured for four consecutive weeks. Blood samples were collected from all the patients, and their clinical severity was determined 1 month after their initial presentation. The clinical severity of CD was determined using the Harvey Bradshaw index (HBI), while the patients with UC completed the SEO clinical activity index (SEOI). The relationships between the disease severity and the means of these four E-CO readings were then compared.

Results: The mean age of the participants was 42.28 ± 14.9 years, and 158 (60.3%) were men. In addition, 27.2% of the UC group and 44% of the CD group were smokers. The mean SEOI score was 145.7 ± 42.0 (min = 90, max = 227), and the mean HBI score was 5.75 ± 3.3 (min = 1, max = 15). Increased CO ppm (OR = -9.047 to 7.654 95% CI) and the number of cigarettes smoked per day (OR = -0.161 to 1.157 95% CI) emerged as independent risk factors for lower SEO scores in the linear regression models (p < 0.001), while the number of cigarettes smoked per day (OR = 0.271 to 1.182% 95 CI) was a risk factor for higher HBI scores (p = 0.022).

Conclusion: UC severity decreased with higher E-CO levels and the mean number of cigarettes smoked, while CD severity increased in line with the mean number of cigarettes smoked.